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Archive for the ‘Chemical Biology and its relations to Metabolic Disease’ Category

Calcium Channel Blocker Potential for Angina

Larry H. Bernstein, MD, FCAP, Curator

LPBI

 

 

Pranidipine    

ANTHONY MELVIN CRASTO, PhD

str1

https://newdrugapprovals.files.wordpress.com/2015/12/str116.jpg

 

File:Pranidipine structure.svg

Pranidipine , OPC-13340, FRC 8411

Acalas®

NDA Filing in Japan

A calcium channel blocker potentially for the treatment of angina pectoris and hypertension.

 

CAS No. 99522-79-9

  • Molecular FormulaC25H24N2O6
  • Average mass 448.468

 

see dipine series………..http://organicsynthesisinternational.blogspot.in/p/dipine-series.html

manidipine

 

PAPER

Der Pharmacia Sinica, 2014, 5(1):11-17

https://newdrugapprovals.files.wordpress.com/2015/12/str113.jpg

pelagiaresearchlibrary.com/der-pharmacia-sinica/vol5-iss1/DPS-2014-5-1-11-17.pdf

 

Names
IUPAC name

methyl (2E)-phenylprop-2-en-1-yl 2,6-dimethyl-4-(3-nitrophenyl)-1,4-dihydropyridine-3,5-dicarboxylate
Other names

2,6-dimethyl-4-(3-nitrophenyl)-1,4-dihydropyridine-3,5-dicarboxylic acid O5-methyl O3-[(E)-3-phenylprop-2-enyl] ester
Identifiers
99522-79-9 Yes
ChEMBL ChEMBL1096842 
ChemSpider 4940726 
Jmol interactive 3D Image
MeSH C048161
PubChem 6436048
UNII 9DES9QVH58 Yes

 

 

 

PATENT SUBMITTED GRANTED
Process for the preparation of 1,4 – dihydropyridines and novel 1,4-dihydropyridines useful as therapeutic agents [US2003230478] 2003-12-18
Advanced Formulations and Therapies for Treating Hard-to-Heal Wounds [US2014357645] 2014-08-19 2014-12-04
METHODS OF TREATING CARDIOVASCULAR AND METABOLIC DISEASES [US2014322199] 2012-08-06 2014-10-30
Protein Carrier-Linked Prodrugs [US2014323402] 2012-08-10 2014-10-30
sGC STIMULATORS [US2014323448] 2014-04-29 2014-10-30
TREATMENT OF ARTERIAL WALL BY COMBINATION OF RAAS INHIBITOR AND HMG-CoA REDUCTASE INHIBITOR [US2014323536] 2012-12-07 2014-10-30
Agonists of Guanylate Cyclase Useful For the Treatment of Gastrointestinal Disorders, Inflammation, Cancer and Other Disorders [US2014329738] 2014-03-28 2014-11-06
METHODS, COMPOSITIONS, AND KITS FOR THE TREATMENT OF CANCER [US2014335050] 2012-05-25 2014-11-13
ROR GAMMA MODULATORS [US2014343023] 2012-09-18 2014-11-20
High-Loading Water-Soluable Carrier-Linked Prodrugs [US2014296257] 2012-08-10 2014-10-02 

 

 

Synthesis, isolation and use of a common key intermediate for calcium antagonist inhibitors

Neelakandan K.a,b, Manikandan H.b , B. Prabhakarana*, Santosha N.a , Ashok Chaudharia *, Mukund Kulkarnic , Gopalakrishnan Mannathusamyb and Shyam Titirmarea
a API Research Centre, Emcure Pharmaceutical Limited, Hinjawadi, Pune, India bDepartment of Chemistry, Annamalai University, Chidhambaram, India cDepartment of Chemistry, Pune University, Pune, India _________________________________________________________________________________

Pelagia Research Library     www.pelagiaresearchlibrary.com      Der Pharmacia Sinica, 2014, 5(1):11-17

 

The compound (3) synthesized from Nitrobenzaldehyde, tertiary butyl acetoacetate and piperidine can be used as a common intermediate for the production of calcium channel blockers like Nicardipine hydrochloride (1) and Pranidipine hydrochloride (2) with high purity.

 

The last twenty years have witnessed discoveries of calcium antagonists associated with multicoated pharmacodynamics potential which include not only antihypertensive and antiarrhythmic effects of the drugs but also action against excessive calcium entry in the cell of cardiovascular system and subsequent cell damage. Among many classes of calcium channel blockers, 1,4-dihydropyrimidine based drug molecules represented by Felodipine, Clevidipine, Benidipine, Nicardipine and Pranidipine are by far the best to reduce systemic vascular resistance and arterial pressure.

The reported synthetic approaches however proceed with complicated work ups, laborious purification procedures, highly expensive chemicals and low overall yields. (Scheme-I).

Synthetic scheme of Nicardipine and Pranidipine In view of the draw backs associated with previous synthetic approaches there is a strong need for environmentfriendly high yielding process applicable to the multi-kilogram production of calcium antagonist inhibitors. Herein, we report a scalable synthesis for Nicardipine hydrochloride (1) and Pranidipine hydrochloride (2) in fairly high overall yield using key intermediate 3-nitro benzylidene acid (3).Compound (3) was synthesized in two steps using 3-nitrobenzaldehyde, tertiary butyl acetoacetate and piperidine as a base to furnish tertiary butyl ester derivative (10). This was followed by hydrolysis of (10) in TFA and DCM to furnish compound (3) which would serve as a precursor for synthesis of versatile calcium antagonist inhibitors (Scheme-II).

Reported routes for synthesis of Benidipine,1,2 Lercanadipine,3-6 Nimodipine,7-11 Barnidipine12-14 and Manidipine15-16 were explored in our laboratory which involve reaction of nitro benzaldehyde with tertiary butyl acetoacetate using piperidine as a base to get tertiary butyl ester derivative (10). This is further treated with respective reagents to get various calcium channel blockers as shown in scheme 4. Since reported procedures involve in-situ generation of intermediate (3) and its reaction with corresponding fragments, it results in the formation of by-products which ultimately decrease the yield and increase the cost of API.

A novel process of manufacturing benzylidine acid derivative (3) was developed. Use of this intermediate was demonstrated by synthesis of Nicardipine and Pranidipine. This protocol may be employed for synthesis of other calcium channel blockers. In conclusion, a highly efficient, reproducible and scalable process for the synthesis of calcium channel blockers has been developed using (3) as the key intermediate.

 

[1] US 63 365 (Kyowa Hakko; appl.15.4.1982; J-prior.17.4.1981). [2] US 4 448 964 (Kyowa Hakko;15.5.1984; J-prior.17.4.1981). [3] Leonardi, A. et al.: Eur. J. Med.Chem. (EJMCA5) 33,399 (1988). [4] EP 153 016 (Recordati Chem. and Pharm.; appl. 21.1.1985; GB-prior. 14.2.1984). [5] US 4 705 797 (Recordati;10.11.1987; GB-prior. 14.2.1984). [6] WO 9 635 668 (Recordati Chem. and Pharm.; appl. 9.5.1996; I-prior. 12.5.1995). [7] DOS 2 117 571 (Bayer; appl. 10.4.1971). [8] DE 2 117 573 (Bayer; prior.10.4.1971) [9] US 3 799 934 (Bayer;26.3.1974;D-prior.10.4.1971). [10] US 3 932 645 (Bayer;13.1.1976;D-prior.10.4.1971). [11] Meyer, H. et al.: Arzneim.-Forsch. (ARZNAD) 31, 407 (1981); 33, 106 (1983). [12] DE 2 904 552 (Yamanouchi Pharm.; appl. 7.2.1979; J-prior.14.2.1978). [13] US 4 220 649 (Yamanouchi;2.9.1980; J-prior.14.2.1978). [14] CN 85 107 590( Faming Zhuanli Sheqing Gonhali S.; appl. 11.10.1985; J-prior.24.1.1985). [15] EP 94 159 (Takeda; appl. 15.4.1983; J-prior. 10.5.1982). [16] US 4 892 875 (Takeda;9.1.1990; J-prior. 10.5.1982, 11.1.1983).

 

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Autocrine selection of GLP-1 binding site

Larry H. Bernstein, MD, FCAP, Curator

LPBI

Update 12/15/2015

TSRI Team Finds Unique Anti-Diabetes Compound

Scientists from The Scripps Research Institute (TSRI) have deployed a powerful new drug discovery technique to identify an anti-diabetes compound with a novel mechanism of action

http://www.technologynetworks.com/HTS/news.aspx?ID=186055

The finding may lead to a new type of diabetes treatment. Just as importantly, it demonstrates the potential of the new technique, which enables researchers to quickly find drug candidates that activate cellular receptors in desired ways.

“In principle, we can apply this technique to hundreds of other receptors like the one we targeted in this study to find disease treatments that are more potent and have fewer side effects than existing therapies. It has been a very productive cross-campus collaboration, so we’re hoping to build on its success as we continue to collaborate on interrogating potential therapeutic targets,” said Patricia H. McDonald, an assistant professor at TSRI’s Jupiter, Florida campus and a senior investigator of the study.

McDonald’s laboratory collaborated on the study with the laboratory of Richard A. Lerner, the Lita Annenberg Hazen Professor of Immunochemistry at TSRI’s La Jolla campus, and with other TSRI groups. Lerner has pioneered techniques for generating and screening large libraries of antibodies or proteins to find new therapies.

In Search of a Better Activator

Three years ago, Lerner and colleagues devised a technique called autocrine selection, which enables scientists to screen very large libraries of molecules to find those that not only bind a given cellular receptor but also activate it to bring about a desired therapeutic effect. Since then, the Lerner laboratory and collaborating scientists have used the technique to find new molecules that block cold virus infection, boost red blood cell production and kill cancer cells, among other effects.

For the new study, Lerner and his laboratory used the technique to target a receptor linked to type 2 diabetes, a life-shortening disease estimated to affect 30 million people in the US alone.

The GLP-1 receptor, as it is known, is expressed by insulin-producing “beta cells” in the pancreas. Several drugs that activate this receptor—drugs called GLP-1 receptor agonists—are already approved for treating type 2 diabetes. In this case, the TSRI team’s aim was to find a molecule that activates the GLP-1 receptor in a unique way.

The GLP-1 receptor belongs to a large class of receptors known as G protein-coupled receptors (GPCRs). Scientists recently have come to understand that when a molecule activates a GPCR, it doesn’t necessarily trigger a single chain of biochemical signals within the cell. In fact, most GPCR agonists trigger signals via multiple distinct pathways—one being via a so-called G protein and another via a protein known as beta-arrestin. In some cases, a “biased agonist” that principally activates just one of these pathways would work better than one that activates both.

In this case, Lerner and his laboratory teamed up with McDonald, an expert on GPCRs and metabolic disease, to find a molecule that would preferentially activate the GLP-1 receptor’s G protein pathway.

To start, researchers in Lerner’s laboratory, including Hongkai Zhang, a senior staff scientist and co-first author of the study, generated a library of candidate molecules—based on a known GLP-1 receptor agonist, Exendin-4, a small protein (peptide) originally found in the venom of Gila monster lizards; a synthetic version of this protein is now used as a type 2 diabetes medication. Zhang created about one million new peptides by randomly varying one end of Exendin-4—the end that normally activates the G protein and beta arrestin pathways.

“The idea was that at least one of these many variants would induce a change in the shape of the GLP-1 receptor that would activate the G-protein pathway without activating the beta arrestin pathway,” Zhang said.

Using the autocrine selection system, Zhang and colleagues rapidly screened these variant peptides and eventually isolated one, P5, that potently and selectively activated the GLP-1 receptor’s G-protein pathway. An initial test in healthy mice showed that P5 worked well at boosting glucose tolerance—at about one-hundredth the dose of Exendin-4 needed for the same effect.

Protein expert Philip E. Dawson, an associate professor at TSRI’s La Jolla campus, synthesized sufficient quantities of P5, and McDonald and her laboratory performed more advanced tests in cultured cells and in mice.

A Different Mechanism

Exendin-4 and and other GLP-1 receptor agonists work in part by strongly stimulating pancreatic beta cells to produce more insulin—which signals muscle and fat cells to draw glucose from the blood, thus lowering blood glucose levels.

McDonald and her team found that although P5 equals or outperforms Exendin-4 in standard mouse models of diabetes, it stimulates insulin production only weakly.

“We didn’t expect that, but in fact, it was a nice finding because less reliance on stimulating insulin could mean less stress on the beta cells,” said Emmanuel Sturchler, staff scientist in the McDonald laboratory and co-first author of the study.

Investigating further, the team found that while the peptide doesn’t make mice fatter or heavier, it triggers the growth of new fat cells. In typical obesity-related diabetes, fat cells grow larger, not more numerous, and as they grow larger, they lose their ability to respond to insulin (insulin resistance). The proliferation of fat cells with P5 was accompanied by signs of increased insulin sensitivity in those cells, suggesting that the peptide works in part by alleviating insulin resistance.

Exendin-4 induces a feeling of satiety, causing mice (and people) to modestly lower food intake and thus lose weight. But the researchers found that P5 lacks this mechanism and appears to have no effect on appetite or weight.

“P5’s mechanisms of action turned out to be quite different from Exendin-4’s, and we think that this finding could lead to new therapeutics,” Sturchler said.

The team will now look for opportunities to develop P5 into a new diabetes drug. The researchers also see this as the first of many discoveries of GPCR-targeting compounds with unique and potentially valuable properties—as well as discoveries in basic GPCR biology.

 

New screening tech at Scripps spotlights diabetes drug candidates

Wednesday, December 9, 2015 | By John Carrol

 

The Scripps Research Institute has used a new drug screening platform to identify a drug which researchers believe has strong potential for treating diabetes.

Working with a technique dubbed autocrine selection, investigators are able to screen molecules in search of targets that can bind to and activate cellular receptors in order to achieve a sought-after drug effect.

In this latest study, published in Nature Communications, the Scripps team went after the GLP-1 receptor, which is already the target of a number of GLP-1 agonists. Scripps, though, wanted to activate the GLP-1 receptor’s G protein pathway.

Hongkai Zhang focused on the GLP-1 agonist Extendin-4, whipping up a million peptides that could alter the end of the protein that activates the G protein and beta arrestin pathways.

“The idea was that at least one of these many variants would induce a change in the shape of the GLP-1 receptor that would activate the G-protein pathway without activating the beta arrestin pathway,” Zhang said.

They then identified the one in a million that improved glucose tolerance at a radically reduced dose of Extendin-4, testing it on mice.

“P5’s mechanisms of action turned out to be quite different from Exendin-4’s, and we think that this finding could lead to new therapeutics,” said Emmanuel Sturchler, a staff scientist in the McDonald laboratory and co-first author of the study.

https://www.scripps.edu/news/press/2015/20151207lerner-mcdonald.html

Scientists from The Scripps Research Institute (TSRI) have deployed a powerful new drug discovery technique to identify an anti-diabetes compound with a novel mechanism of action.

The finding, which appeared online ahead of print in Nature Communications, may lead to a new type of diabetes treatment. Just as importantly, it demonstrates the potential of the new technique, which enables researchers to quickly find drug candidates that activate cellular receptors in desired ways.

“In principle, we can apply this technique to hundreds of other receptors like the one we targeted in this study to find disease treatments that are more potent and have fewer side effects than existing therapies. It has been a very productive cross-campus collaboration, so we’re hoping to build on its success as we continue to collaborate on interrogating potential therapeutic targets,” said Patricia H. McDonald, an assistant professor at TSRI’s Jupiter, Florida campus and a senior investigator of the study.

 

‘Fingerprints’ for Major Drug Development Targets

For the first time, scientists from the Florida campus of The Scripps Research Institute (TSRI) have created detailed “fingerprints” of a class of surface receptors that have proven highly useful for drug development.

http://www.technologynetworks.com/HTS/news.aspx?ID=185860

These detailed “fingerprints” show the surprising complexity of how these receptors activate their binding partners to produce a wide range of signaling actions.

The study focuses on interactions of G protein-coupled receptors (GPCRs) with their signaling mediators known as G proteins. GPCRs—currently accounting for about 40 percent of all prescription pharmaceuticals on the market—play key roles in many physiological functions because they transmit signals from outside the cell to the interior. When an outside substance binds to a GPCR, it activates a G protein inside the cell to release components and create a specific cellular response.

“Until now, it was generally believed that GPCRs are very selective, activating only a few G proteins they were designed to work with,” said TSRI Associate Professor Kirill Martemyanov, who led the study. “It turns out the reality is much more complex.”

Ikuo Masuho, a senior research associate in the Martemyanov lab, added, “Our imaging technology opens a unique avenue of developing drugs that would precisely control complex GPCR-G protein coupling, maximizing therapeutic potency by activating G proteins that contribute to therapeutic efficacy while inhibiting other G proteins that cause adverse side effects.”

The study found that individual GPCRs engage multiple G proteins with varying efficacy and rates, much like a dance where the most desirable partner, the GPCR, is surrounded by 14 suitors all vying for attention. The results, as in any dance, depend on which G proteins bind to the receptor—and for how long. The same receptor changes G protein partners—and the signaling outcome—depending on the action of the signal received from outside of the cell.

This finding was made possible by novel imaging technology used by the Martemyanov lab to monitor G protein activation in live cells. Using a pair of light-emitting proteins, one attached to the G protein, the other attached to what’s known as a reporter molecule, Martemyanov and his colleagues were able to measure simultaneously both the signal and activation rates of most G proteins present in the body.

“Our approach looks at 14 different types of G proteins at once—and we only have 16 in our bodies,” he said. “This is as close as it can get to what is actually happening in real time.”

In the accompanying commentary in Science Signaling, Alan Smrcka, a professor at University of Rochester Medical School and a prominent GPCR researcher, wrote, “[The findings] suggest the power of the GPCR fingerprinting approach, in that it could predict the G protein coupling specificity of a GPCR in a native system, which was previously undetected by conventional analysis. This could be very helpful for identifying previously unappreciated signaling pathways downstream of individual GPCRs that could be useful therapeutically or identified as potential side effects of GPCRs.”

 

Long-Acting Glucagon-Like Peptide 1 Receptor Agonists  

A review of their efficacy and tolerability

Alan J. Garber, MD, PHD

Diabetes Care May 2011; 34(Supplement 2): S279-S284    http://dx.doi.org/10.2337/dc11-s231

Targeting the incretin system has become an important therapeutic approach for treating type 2 diabetes. Two drug classes have been developed: glucagon-like peptide (GLP)-1 receptor agonists and dipeptidyl peptidase 4 (DPP-4) inhibitors. Clinical data have revealed that these therapies improve glycemic control while reducing body weight (GLP-1 receptor agonists, specifically) and systolic blood pressure (SBP) in patients with type 2 diabetes. Furthermore, incidence of hypoglycemia is relatively low with these treatments (except when used in combination with a sulfonylurea) because of their glucose-dependent mechanism of action. There are currently two GLP-1 receptor agonists available (exenatide and liraglutide), with several more currently being developed. This review considers the efficacy and safety of both the short- and long-acting GLP-1 receptor agonists. Head-to-head clinical trial data suggest that long-acting GLP-1 receptor agonists produce superior glycemic control when compared with their short-acting counterparts. Furthermore, these long-acting GLP-1 receptor agonists were generally well tolerated, with transient nausea being the most frequently reported adverse effect.

Careful consideration should be given to the selection of therapies for managing type 2 diabetes. In particular, antidiabetic agents that offer improved glycemic control without increasing cardiovascular risk factors or rates of hypoglycemia are warranted. At present, many available treatments for type 2 diabetes fail to maintain glycemic control in the longer term because of gradual disease progression as β-cell function declines. Where sulfonylureas or thiazolidinediones (common oral antidiabetic drugs) are used, the risk of hypoglycemia and weight gain can increase (1,2). The development of new therapies for the treatment of type 2 diabetes that, in addition to maintaining glycemic control, could reduce body weight and hypoglycemia risk (3,4), may help with patient management. Indeed, guidelines have been developed that support the consensus that blood pressure, weight reduction, and avoidance of hypoglycemic events should be targeted in type 2 diabetes management alongside glycemic targets. For example, the American Diabetes Association (ADA) defines multiple goals of therapy that include A1C <7.0% and SBP <130 mmHg and no weight gain (or, in the case of obese subjects, weight loss) (5). In particular, incretin-based therapies (GLP-1 receptor agonists, specifically) can help meet these new targets by offering weight reduction, blood pressure reduction, and reduced hypoglycemia in addition to glycemic control.

WHAT IS GLP-1?

The incretin effect, responsible for 50–70% of total insulin secretion after oral glucose administration, is defined as the difference in insulin secretory response from an oral glucose load compared with intravenous glucose administration (6) (Supplementary Fig. 1).

There are two naturally occurring incretin hormones that play a role in the maintenance of glycemic control: glucose-dependent insulinotropic polypeptide and GLP-1, both of which have a short half-life because of their rapid inactivation by DPP-4 (7). In patients with type 2 diabetes, the incretin effect is reduced or, in some cases, absent (8). In particular, the insulinoptropic action of glucose-dependent insulinotropic polypeptide is lost in patients with type 2 diabetes. However, it has been shown that, after administration of pharmacological levels of GLP-1, the insulin secretory function can be restored in this population (9), and thus GLP-1 has become an important target for research into new therapies for type 2 diabetes.

GLP-1 has multiple physiological effects that make it an attractive candidate for type 2 diabetes therapy. It increases insulin secretion while inhibiting glucagon release, but only when glucose levels are elevated (6,10), thus offering the potential to lower plasma glucose while reducing the likelihood of hypoglycemia. Furthermore, gastric emptying is delayed (10) and food intake is decreased after GLP-1 administration. Indeed, in a 6-week study investigating continuous GLP-1 infusion, patients with type 2 diabetes achieved a significant weight loss of 1.9 kg and a reduction in appetite from baseline compared with patients receiving placebo, where there was no significant change in weight or appetite (11). Preclinical studies reveal other potential benefits of GLP-1 receptor agonist treatment in individuals with type 2 diabetes, which include the promotion of β-cell proliferation (12) and reduced β-cell apoptosis (13). These preclinical results indicate that GLP-1 could be beneficial in treating patients with type 2 diabetes. However, because native GLP-1 is rapidly inactivated and degraded by the enzyme DPP-4 and has a very short half-life of 1.5 min (14), to achieve the clinical potential for native GLP-1, patients would require 24-h administration of native GLP-1 (15). Because this is impractical as a therapeutic option for type 2 diabetes, it was necessary to develop longer-acting derivatives of GLP-1.

DEVELOPMENT OF DPP-4–RESISTANT GLP-1 RECEPTOR AGONISTS

Two classes of incretin-based therapy have been developed to overcome the clinical limitations of native GLP-1: GLP-1 receptor agonists (e.g., liraglutide and exenatide), which exhibit increased resistance to DPP-4 degradation and thus provide pharmacological levels of GLP-1, and DPP-4 inhibitors (e.g., sitagliptin, vildagliptin, saxagliptin), which reduce endogenous GLP-1 degradation, thereby providing physiological levels of GLP-1. In this review, we focus on the GLP-1 receptor agonist class of incretin-based therapies. The efficacy and tolerability of the DPP-4 inhibitors have been reviewed elsewhere (16). Two GLP-1 receptor agonists are licensed at present in Europe, the U.S., and Japan: exenatide (Byetta, Eli Lilly) (17) and liraglutide (Victoza, Novo Nordisk) (18). For the purposes of this review, we refer to “short-acting” GLP-1 receptor agonists as those agents having duration of action of <24 h and “long-acting” as those agents with duration of action >24 h (Table 1).

….. more        http://care.diabetesjournals.org/content/34/Supplement_2/S279.full.pdf+html

 

Autocrine selection of a GLP-1R G-protein biased agonist with potent antidiabetic effects

Hongkai ZhangEmmanuel SturchlerJiang ZhuAinhoa NietoPhilip A. Cistrone,…., Patricia H. McDonald & Richard A. Lerner
Nature Communications Dec 2015; 6(8918)
       
     http://dx.doi.org:/10.1038/ncomms9918

Glucagon-like peptide-1 (GLP-1) receptor (GLP-1R) agonists have emerged as treatment options for type 2 diabetes mellitus (T2DM). GLP-1R signals through G-protein-dependent, and G-protein-independent pathways by engaging the scaffold protein β-arrestin; preferential signalling of ligands through one or the other of these branches is known as ‘ligand bias’. Here we report the discovery of the potent and selective GLP-1R G-protein-biased agonist, P5. We identified P5 in a high-throughput autocrine-based screening of large combinatorial peptide libraries, and show that P5 promotes G-protein signalling comparable to GLP-1 and Exendin-4, but exhibited a significantly reduced β-arrestin response. Preclinical studies using different mouse models of T2DM demonstrate that P5 is a weak insulin secretagogue. Nevertheless, chronic treatment of diabetic mice with P5 increased adipogenesis, reduced adipose tissue inflammation as well as hepatic steatosis and was more effective at correcting hyperglycemia and lowering hemoglobin A1clevels than Exendin-4, suggesting that GLP-1R G-protein-biased agonists may provide a novel therapeutic approach to T2DM.

Figure 1: Autocrine-based system for selection of agonists from large combinatorial peptide libraries

Autocrine-based system for selection of agonists from large combinatorial peptide libraries.

(a) Schematic representation of the peptide libraries. (b) Schematic representation of the membrane-tethered Exendin-4 (top) and FACS analysis of mCherry and GFP expression 2 days after transduction of HEK293-GLP-1R-GFP cells with the membrane-tethered Exendin-4 displaying different linker size (bottom). (c) Schematic representation of the autocrine-based selection of combinatorial peptide library. The lentivirus peptide libraries are preparred from lentiviral plasmids (step 1). The CRE-responsive GLP-1R reporter cell line is transduced with lentiviral library (step 2). GFP expressing cells are sorted (step 3) and peptide-encoding genes are amplified from genomic DNA of sorted cells to make the library for the next selection round (step 4). After iterative rounds of selection, enriched peptide sequences are analysed by deep sequencing (step 5). (d) Enrichment of GFP positive cells during three rounds of FACS selection. (e) N termini sequences of top 13 peptides (frequency>1.0% representation).

 

Type 2 diabetes mellitus (T2DM) is a complex metabolic disorder characterized by hyperglycaemia arising from a combination of insufficient insulin secretion together with the development of insulin resistance. The incretin, glucagon-like peptide-1 (GLP-1) is an endogenous peptide hormone secreted from intestinal endocrine cells in response to food intake1. GLP-1 lowers postprandial glucose excursion by potentiating glucose-stimulated insulin secretion from pancreatic β-cells and has also recently been shown to promote β-cell survival in rodents2. In addition, GLP-1 exerts extra-pancreatic actions such as promoting gastric emptying, weight loss and increasing insulin sensitivity in peripheral tissues3. Hence, incretin-based therapies represent a strategy for the treatment of T2DM.

GLP-1 exerts its action through the GLP-1 receptor (GLP-1R)4 expressed in the pancreas, other peripheral tissues, and the central nervous system. Activation of GLP-1R triggers Gαs-protein coupling leading to an elevation of cyclic AMP (cAMP), modulates intracellular calcium concentration5 and induces β-arrestin recruitment6, 7. Historically, β-arrestins were believed to serve an exclusive role in G-protein coupled receptor (GPCR) desensitization8. However, it has since been shown that β-arrestins can also function to activate signalling cascades9, 10. In this regard, in the pancreatic β-cell, elevation of both cAMP and cytosolic Ca2+ and β-arrestin signalling downstream of GLP-1R activation are critical events in promoting glucose-dependent insulin secretion.

Recently, the concept of ‘functional selectivity’ or ‘ligand bias’ has emerged whereby ligand binding promotes engagement of only a particular subset of the full GPCR signalling repertoire to the exclusion of others11. A better understanding of GLP-1R pleiotropic signalling and the underlying physiological consequences might provide new avenues for the development of drugs with novel modes of action that have the potential to provide greater therapeutic value while possibly avoiding unwanted side effects12, 13. Therefore we developed an autocrine-based system, to screen large and diverse, combinatorial peptide libraries containing up to 100 million different members with the aim of identifying potent, selective, G-protein-biased GLP-1R agonists. We identified one such ligand, designated P5 and have characterized its in vitro pharmacological phenotype, and explored its therapeutic potential.

P5 is a selective and potent G-protein-biased GLP-1R agonist

To assess potential signalling bias, the active peptides were further characterized in vitro using distinct assays that monitor receptor proximal signals. Cell-based assays for Gαs-protein (cAMP production), Gαq-protein (intracellular Ca2+ mobilization) and β-arrestin (1 and 2) signalling were used to determine the potency (EC50; effector concentration for half-maximum response) and maximal efficacy (Emax (%)) of peptides relative to the reference ligand Ex4 (Table 1). Peptides P1, P2, P5 and P10 all stimulated cAMP production. However, only P5 functioned as a full agonist (Emax=100%) displaying sub-nanomolar potency at both the human (hGLP-1R) and mouse receptor (mGLP-1R) (Fig. 2a,b; Table 1). The P5 EC50 was similar to the endogenous ligand GLP-1 but was slightly right shifted when compared with the reference peptide Ex4 (Fig. 2a,b; Table 1). Importantly, P5-induced cAMP production was inhibited by the selective GLP-1R antagonist Ex 9–39 in a concentration-dependent manner (Supplementary Fig. 1a,b). In addition, P5-induced cAMP production was negligible in HEK293 cells expressing the human glucagon receptor (Supplementary Fig. 1c). These data suggest that P5 selectively interacts with the GLP-1R.

 

In line with previous reports43, 44, 45 our data support the notion that non β-cell actions of GLP-1 agonists can improve glycaemic control. Importantly, GLP-1R is expressed in adipose tissue, in both the stromal vascular and the adipocyte fraction and its expression level has been found to correlate with the degree of insulin resistance46. In addition, the GLP-1 peptide has been reported to regulate adipogenesis in vitro47, 48. Given that P5, a G-protein-biased agonist with a severely blunted β-arrestin response has less propensity to induce GLP-1R desensitization, sustained activation of the receptor in adipose tissue may lead to the changes we observed in eWAT. Consistent with this notion, increased expression of adipogenic genes and a decrease in resistin expression was reported in β-arrestin 1 knockout mice49. Nevertheless, considering the multitude of metabolic pathways regulated by β-arrestin, further studies are warranted to determine the role of β-arrestin signalling downstream of GLP-1R activation in adipogenesis. Additionally, we found that chronic treatment with P5 increased circulating level of GIP to a greater extent than Ex4. Several studies demonstrated that GIP acts as an insulin sensitizer in adipocytes and disruption of the GIP/GIP-R axis has been reported in insulin-resistant states such as obesity50, 51. Interestingly, PPARγ activation was shown to increase GIP-R levels during adipocyte differentiation52. Thus, by increasing GIP and PPARγ levels, P5 chronic treatment may restore GIP/GIP-R signalling in adipocytes. Furthermore, previous studies have demonstrated that the simultaneous activation of the GLP-1R and the GIP-R results in enhanced glycaemic control, and lower HbA1c levels in human and rat, when compared with GLP-1R alone53, suggesting a GIP and GLP-1 synergism. Thus, the superior glycaemic control observed with the G-protein-biased agonist may result from P5-induced increases in GIP level and concomitant receptor activation. In addition, the GLP-1R can form homodimers as well as ligand-induced heterodimers with the GIP-R54. It is conceivable, that P5 may promote the formation of new and pharmacologically distinct homo/heterodimers displaying different signalling capacity. However, further studies are required to delineate more precisely the molecular and cellular mechanisms and the consequences of P5-induced increase in GIP levels.

In summary, high-throughput autocrine-based functional screening of combinatorial peptide libraries enabled the discovery of a high potency G-protein-biased GLP-1R agonist demonstrating new pharmacological virtues. In a series of translational preclinical studies we demonstrate that P5 is a weak insulin secretagogue yet displays superior antidiabetic effect (Fig. 7). Thus, GLP-1R G-protein-biased ligands may offer new and unappreciated advantages in the context of chronic treatment such as promoting adipocyte hyperplasia, restoring insulin responsiveness and long-term glycaemic control while preserving pancreatic β-cell function by minimizing the insulin secretory burden.

 

Figure 7: Schematic depicting the identification and characterization of a novel GLP-1R-biased agonist.

Schematic depicting the identification and characterization of a novel GLP-1R-biased agonist.

Using an autocrine-based system coupled to FACS, we screened large, diverse, combinatorial peptide libraries and identified P5, a potent and selective G-protein-biased GLP-1R agonist. P5 displayed a decreased insulinotropic effect, yet significantly improved glucose tolerance and insulin responsiveness by promoting white adipocyte tissue hyperplasia.

 

Exendin-4 Is a High Potency Agonist and Truncated Exendin-(9-39)- amide an Antagonist at the Glucagon-like Peptide 1-(7-36)-amide Receptor of Insulin-secreting ,&Cells*

Riidiger Goke, Hans-Christoph Fehmann, Thomas LinnS, Harald Schmidt, Michael Krause9, John EngT, and Burkhard GokeII
J Biol Chem  Sept 1993;268(26):19650-19655      http://www.jbc.org/content/268/26/19650.full.pdf

Exendin-4 purified from Heloderma suspecturn venom shows structural relationship to the important incretin hormone glucagon-like peptide 1-(7-36)- amide (GLP-1). We demonstrate that exendin-4 and truncated exendin-(9-39)-amide specifically interact with the GLP-1 receptor on insulinoma-derived cells and on lung membranes. Exendin-4 displaced “‘IGLP- 1, and unlabeled GLP- 1 displaced lZ6I-exendin-4 from the binding site at rat insulinoma-derived RINmSF cells. Exendin-4 had, like GLP-1, a pronounced effect on intracellular CAMP generation, which was reduced by exendin-(9-39)-amide. When combined, GLP-1 and exendin-4 showed additive action on CAMP. They each competed with the radiolabeled version of the other peptide in cross-linking experiments. The apparent molecular mass of the respective ligand-binding protein complex was 63,000 Da. Exendin-(9-39)-amide abolished the cross-linking of both peptides. Exendin-4, like GLP-1, stimulated dose dependently the glucose-induced insulin wcretion in isolated rat islets, and, in mouse insulinoma TC-1 cells, both peptides stimulated the proinsulin gene expression at the level of transcription. Exendin- (9-39)-amide reduced these effects. In conclusion, exendin-4 is an agonist and exendin-(9-39)-amide is a specific GLP- 1 receptor antagonist.

 

Glucagon-like peptide-1 receptor agonists for the treatment of type 2 diabetes mellitus

Kathleen Dungan, MDAnthony DeSantis, MD
http://www.uptodate.com/contents/glucagon-like-peptide-1-receptor-agonists-for-the-treatment-of-type-2-diabetes-mellitus

Despite advances in options for the treatment of diabetes, optimal glycemic control is often not achieved. Hypoglycemia and weight gain associated with many antidiabetic medications may interfere with the implementation and long-term application of “intensive” therapies [1]. Current treatments have centered on increasing insulin availability (either through direct insulin administration or through agents that promote insulin secretion), improving sensitivity to insulin, delaying the delivery and absorption of carbohydrate from the gastrointestinal tract, or increasing urinary glucose excretion.

Glucagon-like peptide-1 (GLP-1)-based therapies (eg, GLP-1 receptor agonists, dipeptidyl peptidase 4 [DPP-4] inhibitors) affect glucose control through several mechanisms, including enhancement of glucose-dependent insulin secretion, slowed gastric emptying, and reduction of postprandial glucagon and of food intake (table 1). These agents do not usually cause hypoglycemia in the absence of therapies that otherwise cause hypoglycemia.

This topic will review the mechanism of action and therapeutic utility of GLP-1 receptor agonists for the treatment of type 2 diabetes mellitus. DPP-4 inhibitors are discussed separately. A general discussion of the initial management of blood glucose and the management of persistent hyperglycemia in adults with type 2 diabetes is also presented separately. (See “Dipeptidyl peptidase 4 (DPP-4) inhibitors for the treatment of type 2 diabetes mellitus”.)

GLUCAGON-LIKE PEPTIDE-1

Glucose homeostasis is dependent upon a complex interplay of multiple hormones: insulin and amylin, produced by pancreatic beta cells; glucagon, produced by pancreatic alpha cells; and gastrointestinal peptides, including glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP; gastric inhibitory polypeptide) (figure 1). Abnormal regulation of these substances may contribute to the clinical presentation of diabetes. The role of GLP-1 in glucose homeostasis is illustrative of the incretin effect, in which oral glucose has a greater stimulatory effect on insulin secretion than intravenous glucose [2]. This effect is mediated by several gastrointestinal peptides, particularly GLP-1, that are released in the setting of a meal and stimulate insulin synthesis and insulin secretion, which does not occur when carbohydrate is administered intravenously.

GLP-1 is produced from the proglucagon gene in L-cells of the small intestine and is secreted in response to nutrients (figure 1) [3]. GLP-1 binds to a specific GLP-1 receptor, which is expressed in various tissues including pancreatic beta cells, pancreatic ducts, gastric mucosa, kidney, lung, heart, skin, immune cells, and the hypothalamus [2,4]. GLP-1 exerts its main effect by stimulating glucose-dependent insulin release from the pancreatic islets [2]. It has also been shown to slow gastric emptying [5], inhibit inappropriate post-meal glucagon release [3,6], and reduce food intake (table 1) [3]. Owing in part to the effects of GLP-1 on slowed gastric emptying and appetite centers in the brain, therapy with GLP-1 and its receptor agonists is associated with weight loss, even among patients without significant nausea and vomiting.

 

Exendin-4, a glucagon-like peptide-1 receptor agonist, reduces Alzheimer disease-associated tau hyperphosphorylation in the hippocampus of rats with type 2 diabetes.
Impaired insulin signaling pathway in the brain in type 2 diabetes (T2D) is a risk factor for Alzheimer disease (AD). Glucagon-like peptide-1 (GLP-1) and its receptor agonist are widely used for treatment of T2D. Here we studied whether the effects of exendin-4 (EX-4), a long-lasting GLP-1 receptor agonist, could reduce the risk of AD in T2D.  RESULTS: The levels of phosphorylated tau protein at site Ser199/202 and Thr217 level in the hippocampus of T2D rats were found to be raised notably and evidently decreased after EX-4 intervention. In addition, brain insulin signaling pathway was ameliorated after EX-4 treatment, and this result was reflected by a decreased activity of PI3K/AKT and an increased activity of GSK-3β in the hippocampus of T2D rats as well as a rise in PI3K/AKT activity and a decline in GSK-3β activity after 4 weeks intervention of EX-4. CONCLUSIONS: These results demonstrate that multiple days with EX-4 appears to prevent the hyperphosphorylation of AD-associated tau protein due to increased insulin signaling pathway in the brain. These findings support the potential use of GLP-1 for the prevention and treatment of AD in individuals with T2D.

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von Willebrand Factor

Larry H. Bernstein, MD, FCAP, Curator

LPBI

 

FDA approves first recombinant von Willebrand factor to treat bleeding episodes

Dr. Anthony Melvin Castro

 

 

12/08/2015 02:44
The U.S. Food and Drug Administration today approved Vonvendi, von Willebrand factor (Recombinant), for use in adults 18 years of age and older who have von Willebrand disease (VWD). Vonvendi is the first FDA-approved recombinant von Willebrand factor, and is approved for the on-demand (as needed) treatment and control of bleeding episodes in adults diagnosed with VWD.
Company Baxalta Inc.
Description Recombinant human von Willebrand factor (vWF)
Molecular Target von Willebrand factor (vWF)
Mechanism of Action
Therapeutic Modality Biologic: Protein
Latest Stage of Development Registration
Standard Indication Bleeding
Indication Details Treat and prevent bleeding episodes in von Willebrand disease (vWD) patients; Treat von Willebrand disease (vWD)
Regulatory Designation U.S. – Orphan Drug (Treat and prevent bleeding episodes in von Willebrand disease (vWD) patients);
EU – Orphan Drug (Treat and prevent bleeding episodes in von Willebrand disease (vWD) patients);
Japan – Orphan Drug (Treat and prevent bleeding episodes in von Willebrand disease (vWD) patients)

 

The U.S. Food and Drug Administration today approved Vonvendi, von Willebrand factor (Recombinant), for use in adults 18 years of age and older who have von Willebrand disease (VWD). Vonvendi is the first FDA-approved recombinant von Willebrand factor, and is approved for the on-demand (as needed) treatment and control of bleeding episodes in adults diagnosed with VWD.

VWD is the most common inherited bleeding disorder, affecting approximately 1 percent of the U.S. population. Men and women are equally affected by VWD, which is caused by a deficiency or defect in von Willebrand factor, a protein that is critical for normal blood clotting. Patients with VWD can develop severe bleeding from the nose, gums, and intestines, as well as into muscles and joints. Women with VWD may have heavy menstrual periods lasting longer than average and may experience excessive bleeding after childbirth.

“Patients with heritable bleeding disorders should meet with their health care provider to discuss appropriate measures to reduce blood loss,” said Karen Midthun, M.D., director of the FDA’s Center for Biologics Evaluation and Research. “The approval of Vonvendi provides an additional therapeutic option for the treatment of bleeding episodes in patients with von Willebrand disease.”

The safety and efficacy of Vonvendi were evaluated in two clinical trials of 69 adult participants with VWD. These trials demonstrated that Vonvendi was safe and effective for the on-demand treatment and control of bleeding episodes from a variety of different sites in the body. No safety concerns were identified in the trials. The most common adverse reaction observed was generalized pruritus (itching).

The FDA granted Vonvendi orphan product designation for these uses.Orphan product designation is given to drugs intended to treat rare diseases in order to promote their development.

Vonvendi is manufactured by Baxalta U.S., Inc., based in Westlake Village, California.

 

von Willebrand Disease

Author: Eleanor S Pollak; Chief Editor: Srikanth Nagalla

Von Willebrand disease (vWD) is a common, inherited, genetically and clinically heterogeneous hemorrhagic disorder caused by a deficiency or dysfunction of the protein termed von Willebrand factor (vWF). Consequently, defective vWF interaction between platelets and the vessel wall impairs primary hemostasis.

vWF, a large, multimeric glycoprotein, circulates in blood plasma at concentrations of approximately 10 mg/mL. In response to numerous stimuli, vWF is released from storage granules in platelets and endothelial cells. It performs two major roles in hemostasis. First, it mediates the adhesion of platelets to sites of vascular injury. Second, it binds and stabilizes the procoagulant protein factor VIII (FVIII). (See Etiology.)

vWD is divided into three major categories: (1) partial quantitative deficiency (type I), (2) qualitative deficiency (type II), and (3) total deficiency (type III). vWD type II is further divided into four variants (IIA, IIB, IIN, IIM), based on characteristics of dysfunctional vWF. These categories correspond to distinct molecular mechanisms, with corresponding clinical features and therapeutic recommendations.

For discussion of vWD in children, see Pediatric Von Willebrand Disease.

http://emedicine.medscape.com/article/206996-overview

 

 

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Nuts and health in aging

Larry H. Bernstein, MD, FCAP, Curator

LPBI

 

 

Nut consumption and age-related disease

Giuseppe GrossoRamon Estruch

MATURITAS · OCT 2015     http://dx.doi.org/10.1016/j.maturitas.2015.10.014

Current knowledge on the effects of nut consumption on human health has rapidly increased in recent years and it now appears that nuts may play a role in the prevention of chronic age-related diseases. Frequent nut consumption has been associated with better metabolic status, decreased body weight as well as lower body weight gain over time and thus reduce the risk of obesity. The effect of nuts on glucose metabolism, blood lipids, and blood pressure are still controversial. However, significant decreased cardiovascular risk has been reported in a number of observational and clinical intervention studies. Thus, findings from cohort studies show that increased nut consumption is associated with a reduced risk of cardiovascular disease and mortality (especially that due to cardiovascular-related causes). Similarly, nut consumption has been also associated with reduced risk of certain cancers, such as colorectal, endometrial, and pancreatic neoplasms. Evidence regarding nut consumption and neurological or psychiatric disorders is scarce, but a number of studies suggest significant protective effects against depression, mild cognitive disorders and Alzheimer’s disease. The underlying mechanisms appear to include antioxidant and anti-inflammatory actions, particularly related to their mono- and polyunsaturated fatty acids (MUFA and PUFA, as well as vitamin and polyphenol content. MUFA have been demonstrated to improve pancreatic beta-cell function and regulation of postprandial glycemia and insulin sensitivity. PUFA may act on the central nervous system protecting neuronal and cell-signaling function and maintenance. The fiber and mineral content of nuts may also confer health benefits. Nuts therefore show promise as useful adjuvants to prevent, delay or ameliorate a number of chronic conditions in older people. Their association with decreased mortality suggests a potential in reducing disease burden, including cardiovascular disease, cancer, and cognitive impairments.

 

Global life expectancy has increased from 65 years in 1990 to about 71 years in 2013 [1]. As life expectancy has increased, the number of healthy years lost due to disability has also risen in most countries, consistent with greater morbidity [2]. Reduction of mortality rates in developed countries has been associated with a shift towards more chronic non-communicable diseases [1]. Cardiovascular diseases (CVDs) and related risk factors, such as hypertension, diabetes mellitus, hypercholesterolemia, and obesity are the top causes of death globally, accounting for nearly one-third of all deaths worldwide [3]. Equally, the estimated incidence, mortality, and disability- adjusted life-years (DALYs) for cancer rose to 14.9 million incident cancer cases, 8.2 million deaths, and 196.3 million DALYs, with the highest impact of prostate and breast cancer in men and women, respectively [4]. Depression is a leading cause of disability worldwide (in terms of total years lost due to disability), especially in high-income countries, increasing from 15th to 11th rank (37% increase) and accounting for 18% of total DALYs (almost 100 million DALYs) [5]. Overall, the global rise in chronic non-communicable diseases is congruent with a similar rise in the elderly population. The proportion of people over the age of 60 is growing faster than any other age group and is estimated to double from about 11% to 22% within the next 50 years [6]. Public health efforts are needed to face this epidemiological and demographic transition, both improving the healthcare systems, as well as assuring a better health in older people. Accordingly, a preventive approach is crucial to dealing with an ageing population to reduce the burden of chronic disease.

In this context, lifestyle behaviors have demonstrated the highest impact for older adults in preventing and controlling the morbidity and mortality due to non- communicable diseases [7]. Unhealthy behaviors, such as unbalanced dietary patterns, lack of physical activity and smoking, play a central role in increasing both cardiovascular and cancer risk [7]. Equally, social isolation and depression in later life may boost health decline and significantly contribute to mortality risk [8]. The role of diet in prevention of disability and death is a well-established factor, which has an even more important role in geriatric populations. Research has focused on the effect of both single foods and whole dietary patterns on a number of health outcomes, including mortality, cardiovascular disease (CVD), cancer and mental health disorders (such as cognitive decline and depression) [9-13]. Plantbased dietary patterns demonstrate the most convincing evidence in preventing chronic non-communicable diseases [14-17]. Among the main components (including fruit and vegetables, legumes and cereals), only lately has attention focused on foods such as nuts. Knowledge on the effect of nut consumption on human health has increased rapidly in recent years. The aim of this narrative review is to examine recent evidence regarding the role of nut consumption in preventing chronic disease in older people.

Tree nuts are dry fruits with an edible seed and a hard shell. The most popular tree nuts are almonds (Prunus amigdalis), hazelnuts (Corylus avellana), walnuts (Juglans regia), pistachios (Pistachia vera), cashews (Anacardium occidentale), pecans (Carya illinoiensis), pine nuts (Pinus pinea), macadamias (Macadamia integrifolia), Brazil nuts (Bertholletia excelsa), and chestnuts (Castanea sativa). When considering the “nut” group, researchers also include peanuts (Arachis hypogea), which technically are groundnuts. Nuts are nutrient dense foods, rich in proteins, fats (mainly unsaturated fatty acids), fiber, vitamins, minerals, as well as a number of phytochemicals, such as phytosterols and polyphenols [18]. Proteins account for about 10-25% of energy, including individual aminoacids, such as L-arginine, which is involved in the production of nitric oxide (NO), an endogenous vasodilatator [19].

The fatty acids composition of nuts involves saturated fats for 415% and unsaturated fatty acids for 30-60% of the content. Unsaturated fatty acids are different depending on the nut type, including monounsaturated fatty acids (MUFA, such as oleic acid in most of nuts, whereas polyunsaturated fatty acids (PUFA, such as alpha-linolenic acid) in pine nuts and walnuts [20]. Also fiber content is similar among most nut types (about 10%), although pine nuts and cashews hold the least content. Vitamins contained in nuts are group B vitamins, such as B6 (involved in many aspects of macronutrient metabolism) and folate (necessary for normal cellular function, DNA synthesis and metabolism, and homocysteine detoxification), as well as tocopherols, involved in anti-oxidant mechanisms [21]. Among minerals contained in vegetables, nuts have an optimal content in calcium, magnesium, and potassium, with an extremely low amount of sodium, which is implicated on a number of pathological conditions, such as bone demineralization, hypertension and insulin resistance[22]. Nuts are also rich in phytosterols, non-nutritive components of certain plant-foods that exert both structural (at cellular membrane phospholipids level) and hormonal (estrogen-like) activities [23]. Finally, nuts have been demonstrated to be a rich source of polyphenols, which account for a key role in their antioxidant and anti-inflammatory effects.

 

Metabolic disorders are mainly characterized by obesity, hypertension, dyslipidemia, and hyperglycemia/ hyperinsulinemia/type-2 diabetes, all of which act synergistically to increase morbidity and mortality of aging population.

Obesity Increasing high carbohydrate and fat food intake in the last decades has contributed significantly to the rise in metabolic disorders. Nuts are energy-dense foods that have been thought to be positively associated with increased body mass index (BMI). As calorie-dense foods, nuts may contain 160–200 calories per ounce. The recommendation from the American Heart  Association to consume 5 servings per week (with an average recommended serving size of 28 g) corresponds to a net increase of 800–1000 calories per week, which may cause weight gain. However, an inverse relation between the frequency of nut consumption and BMI has been observed in large cohort studies [24]. Pooling the baseline observations of BMI by category of nut consumption in 5 cohort studies found a significant decreasing trend in BMI values with increasing nut intake [24]. While the evidence regarding nut consumption and obesity is limited, findings so far are encouraging [25, 26]. When the association between nut consumption and body weight has been evaluated longitudinally over time, nut intake was associated with a slightly lower risk of weight gain and obesity [25]. In the Nurses’ Health Study II (NHS II), women who eat nuts ≥2 times per week had slightly less weight gain (5.04 kg) than did women who rarely ate nuts (5.55 kg) and marginally significant 23% lower risk of obesity after 9-year follow-up [25]. Further evaluation of the NHS II data and the Physicians’ Health Study (PHS) comprising a total of 120,877 US women and men and followed up to 20 years revealed that 4-y weight change was inversely associated with a 1-serving increment in the intake of nuts (20.26 kg) [27]. In the “Seguimiento Universidad de Navarra” (SUN) cohort study, a significant decreased weight change has been observed over a period of 6 years [26]. After adjustment for potential confounding factors the analysis was no longer significant, but overall no weight gain associated with >2 servings per week of nuts has been observed. Finally, when considering the role of the whole diet on body weight, a meta-analysis of 31 clinical trials led to the conclusion of a null effect of nut intake on body weight, BMI, and waist circumference [28].

Glucose metabolism and type-2 diabetes The association between nut consumption and risk of type-2 diabetes in prospective cohort studies is controversial [29-32]. A pooled analysis relied on the examination of five large cohorts, including the NHS, the Shanghai Women’s Health Study, the Iowa Women’s Health Study, and the PHS, and two European studies conducted in Spain (the PREDIMED trial) and Finland including a total of more than 230,000 participants and 13,000 cases, respectively. Consumption of 4 servings per week was associated with 13% reduced risk of type-2 diabetes without effect modification by age [29]. In contrast, other pooled analyses showed non-significant reduction of risk for increased intakes of nuts, underlying that the inverse association between the consumption of nuts and diabetes was attenuated after adjustment for confounding factors, including BMI [30]. However, results from experimental studies showed promising results. Thus, nut consumption has been demonstrated to exert beneficial metabolic effects due to their action on post-prandial glycemia an insulin sensitivity. A number of RCTs have demonstrated positive effects of nut consumption on post-prandial glycemia in healthy individuals [33-38]. Moreover, a meta-analysis of RCTs on the effects of nut intake on glycemic control in diabetic individuals including 12 trials and a total of 450 participants showed that diets with an emphasis on nuts (median dose = 56 g/d) significantly lowered HbA1c (Mean Difference [MD] : -0.07%; 95% confidence interval [CI]: -0.10, -0.03%; P = 0.0003) and fasting glucose (MD : -0.15 mmol/L; 95% CI: -0.27, -0.02 mmol/L; P = 0.03) compared with control diets [39]. No significant treatment effects were observed for fasting insulin and homeostatic model assessment (HOMA-IR), despite the direction of effect favoring diet regimens including nuts.

Blood lipids and hypertension Hypertension and dyslipidemia are major risk factors for CVD. Diet alone has a predominant role in blood pressure and plasma lipid homeostasis. One systematic review [40] and 3 pooled quantitative analyses of RCTs [41-43] evaluated the effects of nut consumption on lipid profiles. A general agreement was relevant on certain markers, as daily consumption of nuts (mean = 67 g/d) induced a pooled reduction of total cholesterol concentration (10.9 mg/dL [5.1% change]), low-density lipoprotein cholesterol concentration (LDL-C) (10.2 mg/dL [7.4% change]), ratio of LDL-C to high-density lipoprotein cholesterol concentration (HDL-C) (0.22 [8.3% change]), and ratio of total cholesterol concentration to HDL-C (0.24 [5.6% change]) (P <0.001 for all) [42]. All meta-analyses showed no significant effects of nut (including walnut) consumption on HDL cholesterol or triglyceride concentrations in healthy individuals [41], although reduced plasma triglyceride levels were found in individuals with hypertriglyceridemia [42]. Interestingly, the effects of nut consumption were dose related, and different types of nuts had similar effects on blood lipid concentrations.

There is only limited evidence from observational studies to suggest that nuts have a protective role on blood pressure. A pooled analysis of prospective cohort studies on nut consumption and hypertension reported a decreased risk associated with increased intake of nuts [32]. Specifically, only a limited number of cohort studies have been conducted exploring the association between nut consumption and hypertension (n = 3), but overall reporting an 8% reduced risk of hypertension for individuals consuming >2 servings per week (Risk Ratio [RR] = 0.92, 95% CI: 0.87-0.97) compared with never/rare consumers, whereas consumption of nuts at one serving per week had similar risk estimates (RR = 0.97, 95% CI: 0.83, 1.13) [32]. These findings are consistent with results obtained in a pooled analysis of 21 experimental studies reporting the effect of consuming single or mixed nuts (in doses ranging from 30 to 100 g/d) on systolic (SBP) and diastolic blood pressure (DBP) [44]. A pooled analysis found a significant reduction in SBP in participants without type2 diabetes [MD: -1.29 mmHg; 95% CI: -2.35, -0.22; P = 0.02] and DBP (MD: -1.19; 95% CI: -2.35, -0.03; P = 0.04), whereas subgroup analyses of different nut types showed that pistachios, but not other nuts, significantly reduced SBP (MD: -1.82; 95% CI: -2.97, -0.67; P = 0.002) and SBP (MD: -0.80; 95% CI: -1.43, -0.17; P = 0.01) [44].

Nut consumption and CVD risk Clustering of metabolic risk factors occurs in most obese individuals, greatly increasing risk of CVD. The association between nut consumption and CVD incidence [29-31] and mortality [24] has been explored in several pooled analyses of prospective studies. The overall risk calculated for CVD on a total of 8,862 cases was reduced by 29% for individuals consuming 7 servings per week (RR = 0.71, 95% CI: 0.59, 0.85) [30]. A meta-analysis including 9 studies on coronary artery disease (CAD) including 179,885 individuals and 7,236 cases, reporting that 1-serving/day increment would reduce risk of CAD of about 20% (RR = 0.81, 95% CI: 0.72, 0.91) [31]. Similar risk estimates were calculated for ischemic heart disease (IHD), with a comprehensive reduced risk of about 25-30% associated with a daily intake of nuts [29, 30]. Findings from 4 prospective studies have been pooled to estimate the association between nut consumption and risk of stroke, and a non-significant/borderline reduced risk was found [29-31, 45]. CVD mortality was explored in a recent meta-analysis including a total of 354,933 participants, 44,636 cumulative incident deaths, and 3,746,534 cumulative person-years [24]. One serving of nuts per week and per day resulted in decreased risk of CVD mortality (RR = 0.93, 95% CI: 0.88, 0.99 and RR =0.61, 95% CI: 0.42, 0.91, respectively], primarily driven by decreased coronary artery disease (CAD) deaths rather than stroke deaths [24]. Overall, all pooled analyses demonstrated a significant association between nut consumption and cardiovascular health. However, it has been argued that nut consumption was consistently associated with healthier background characteristics reflecting overall healthier lifestyle choices that eventually lead to decreased CVD mortality risk.

Nut consumption and cancer risk Cancer is one of the leading causes of death in the elderly population. After the evaluation of the impact on cancer burden of food and nutrients, it has been concluded that up to one third of malignancies may be prevented by healthy lifestyle choices. Fruit and vegetable intake has been the focus of major attention, but studies on nut consumption and cancer are scarce. A recent metaanalysis pooled together findings of observational studies on cancer incidence, including a total of 16 cohort and 20 casecontrol studies comprising 30,708 cases, compared the highest category of nut consumption with the lowest category and found a lower risk of any cancer of 25% (RR = 0.85, 95% CI: 0.86, 0.95) [46]. When the analysis was conducted by cancer site, highest consumption of nuts was associated with decreased risk of colorectal (RR = 0.76, 95% CI: 0.61, 0.96), endometrial (RR = 0.58, 95% CI: 0.43, 0.79), and pancreatic cancer (RR = 0.71, 95% CI: 0.51, 0.99), with only one cohort study was conducted on the last [46]. The potential protective effects of nut consumption on cancer outcomes was supported also by pooled analysis of 3 cohort studies [comprising the PREDIMED, the NHS, the HPS, and the Health Professionals Follow-Up Study (HPFS) cohorts] showing a decreased risk of cancer death for individuals consuming 3-5 servings of nuts per week compared with never eaters (RR = 0.86, 95% CI: 0.75, 0.98) [24]. The analysis was recently updated by including results from the Netherlands Cohort Study reaching a total of 14,340 deaths out of 247,030 men and women observed, confirming previous results with no evidence of between-study heterogeneity (RR = 0.85, 95% CI: 0.77, 0.93) [47]. However, a dose- response relation showed the non-linearity of the association, suggesting that only moderate daily consumption up to 5 g reduced risk of cancer mortality, and extra increased intakes were associated with no further decreased risk.

Nut consumption and affective/cognitive disorders Age-related cognitive decline is one of the most detrimental health problems in older people. Cognitive decline is a paraphysiological process of aging, but timing and severity of onset has been demonstrated to be affected by modifiable lifestyle factors, including diet. In fact, the nature of the age- related conditions leading to a mild cognitive impairment (MCI) differs by inflammation-related chronic neurodegenerative diseases, such as dementia, Alzheimer’s disease, Parkinson’s disease and depression. Evidence restricted to nut consumption alone is scarce, but a number of studies have been conducted on dietary patterns including nuts as a major component. A pooled analysis synthesizing findings of studies examining the association between adherence to a traditional Mediterranean diet and risk of depression (n = 9), cognitive decline (n = 8), and Parkinson’s disease (n = 1) showed a reduction of risk of depression (RR = 0.68, 95% CI: 0.54, 0.86) and cognitive impairment (RR = 0.60, 95% CI: 0.43, 0.83) in individuals with increased dietary adherence [10].

The study that first found a decreased risk of Alzheimer’s disease in individuals highly adherent to the Mediterranean diet was conducted in over 2,000 individuals in the Washington/Hamilton Heights-Inwood Columbia Aging Project (WHICAP), a cohort of non-demented elders aged 65 and older living in a multi-ethnic community of Northern Manhattan in the US (Hazard Ratio [HR] = 0.91, 95% CI: 0.83, 0.98) [48]. These results have been replicated in further studies on the Mediterranean diet, however nut consumption was not documented [49, 50]. A number of observational studies also demonstrated a significant association between this dietary pattern and a range of other cognitive outcomes, including slower global cognitive decline [51]. However, evidence from experimental studies is limited to the PREDIMED trial, providing interesting insights on the association between the Mediterranean diet supplemented with mixed nuts and both depression and cognitive outcomes. Regarding depression, the nutritional intervention with a Mediterranean diet supplemented with nuts showed a lower risk of about 40% in participants with type-2 diabetes (RR = 0.59, 95% CI: 0.36, 0.98) compared with the control diet [52]. However the effect was not significant in the whole cohort overall [52]. Regarding cognitive outcomes after a mean follow-up of 4.1 years, findings from the same trial showed significant improvements in memory and global cognition tests for individuals allocated to the Mediterranean diet supplemented with nuts [adjusted differences: -0.09 (95% CI: -0.05, 0.23), P = 0.04 and -0.05 (95% CI: -0.27, 0.18), P = 0.04, respectively], compared to control group, showing that Mediterranean diet plus mixed nuts is associated with improved cognitive function [53].

 

Potential mechanisms of protection of nut consumption Despite the exact mechanisms by which nuts may ameliorate human health being largely unknown, new evidence has allowed us to start to better understand the protection of some high-fat, vegetable, energy-dense foods such as nuts. Non- communicable disease burden related with nutritional habits is mainly secondary to exaggerated intakes of refined sugars and saturated fats, such as processed and fast- foods. Nuts provide a number of nutrient and non-nutrient compounds and it is only recently that scientists have tried to examine their effects on metabolic pathways.

Metabolic and cardiovascular protection With special regard to body weight and their potential effects in decreasing the risk of obesity (or weight gain, in general), nuts may induce satiation (reduction in the total amount of food eaten in a single meal) and satiety (reduction in the frequency of meals) due to their content in fibers and proteins, which are associated with increased release of glucagon-like protein 1 (GLP-1) and cholecystokinin (CCK), gastrointestinal hormones with satiety effects [54, 55]. The content in fiber of nuts may also increase thermogenesis and resting energy expenditure, and reduce post- prandial changes of glucose, thus ameliorating inflammation and insulin resistance. Moreover, the specific content profile of MUFA and PUFA provides readily oxidized fats than saturated or trans fatty acids, leading to reduced fat accumulation [56, 57]. The beneficial effects of nuts toward glucose metabolism may be provided by their MUFA content that improves the efficiency of pancreatic beta-cell function by enhancing the secretion of GLP1, which in turn helps the regulation of postprandial glycemia and insulin sensitivity [58]. MUFA and PUFA are also able to reduce serum concentrations of the vasoconstrictor thromboxane 2, which might influence blood pressure regulation. Together with polyphenols and anti-oxidant vitamins, nuts may also ameliorate inflammatory status at the vascular level, reducing circulating levels of soluble cellular adhesion molecules, such as intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), and E-selectin, which are released from the activated endothelium and circulating monocytes [59]. Moreover, nuts may improve vascular reactivity due to their content in L-arginine, which is a potent precursor of the endogenous vasodilator nitric oxide. Nuts content in microelements is characterized by a mixture that may exert a direct effect in modulating blood pressure, including low content of sodium and richness in magnesium, potassium and calcium, which may interact to beneficially influence blood pressure
Despite the exact mechanisms by which nuts may ameliorate human health being largely unknown, new evidence has allowed us to start to better understand the protection of some high-fat, vegetable, energy-dense foods such as nuts. Non- communicable disease burden related with nutritional habits is mainly secondary to exaggerated intakes of refined sugars and saturated fats, such as processed and fast- foods. Nuts provide a number of nutrient and non-nutrient compounds and it is only recently that scientists have tried to examine their effects on metabolic pathways.

Cancer protection The potential mechanisms of action of nuts that may intervene in the prevention of cancer have not been totally elucidated. Numerous hypotheses have been proposed on the basis of basic research exploring the antioxidant and anti-inflammatory compounds characterizing nuts [61]. Vitamin E can regulate cell differentiation and proliferation, whereas polyphenols (particularly flavonoids such as quercetin and stilbenes such as resveratrol) have been shown to inhibit chemically-induced carcinogenesis [62]. Polyphenols may regulate the inflammatory response and immunological activity by acting on the formation of the prostaglandins and pro-inflammatory cytokines, which may be an important mechanism involved in a number of cancers, including colorectal, gastric, cervical and pancreatic neoplasms [62]. Among other compounds contained in nuts, dietary fiber may exert protective effects toward certain cancers (including, but not limited to colorectal cancer) by the aforementioned metabolic effects as well as increasing the volume of feces and anaerobic fermentation, and reducing the length of intestinal transit. As a result, the intestinal mucosa is exposed to carcinogens for a reduced time and the carcinogens in the colon are diluted [62]. Finally, there is no specific pathway demonstrating the protective effect of PUFA intake against cancer, but their interference with cytokines and prostaglandin metabolism may inhibit a state of chronic inflammation that may increase cancer risk [63].

Cognitive aging and neuro-protection There is no universal mechanism of action for nuts with regard to age-related conditions. A number of systemic biological conditions, such as oxidative stress, inflammation, and reduced cerebral blood flow have been considered as key factors in the pathogenesis of both normal cognitive ageing and chronic neurodegenerative disease [64]. Nuts, alone or as part of healthy dietary patterns, may exert beneficial effects due to their richness in antioxidants, including vitamins, polyphenols and unsaturated fatty acids, that may be protective against the development of cognitive decline and depression [65, 66]. Both animal studies and experimental clinical trials demonstrated vascular benefits of nuts, including the aforementioned lowering of inflammatory markers and improved endothelial function, which all appear to contribute to improved cognitive function [67]. The antioxidant action may affect the physiology of the ageing brain directly, by protecting neuronal and cell-signaling function and maintenance. Moreover, certain compounds contained in nuts may directly interact with the physiology and functioning of the brain. For instance, walnuts are largely composed of PUFA, especially ALA, which have been suggested to induce structural change in brain areas associated with affective experience [66]. Moreover, PUFA have been associated with improved symptoms in depressed patients, suggesting an active role in the underlying pathophysiological mechanisms [68]. Thus, the mechanisms of action of nut consumption on age-related cognitive and depressive disorders are complex, involving direct effects on brain physiology at the neuronal and cellular level and indirect effects by influencing inflammation.

 

Summary From an epidemiological point of view, nut eaters have been associated with overall healthier lifestyle habits, such as increased physical activity, lower prevalence of smoking, and increased consumption of fruits and vegetables [24]. These variables represent strong confounding factors in determining the effects of nuts alone on human health and final conclusions cannot be drawn. Nevertheless, results from clinical trials are encouraging. Nuts show promise as useful adjuvants to prevent, delay or ameliorate a number of chronic conditions in older people.

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HDL oxidation in type 2 diabetic patients

Larry H. Bernstein, MD, FCAP, Curator

LPBI

 

 

 

 

High-density lipoprotein oxidation in type 2 diabetic patients and young patients with premature myocardial infarction

G. SartoreaR. SeragliabS. Burlinaa, , A. BolisaR. MarinaE. ManzatoaE. RagazzicP. TraldibA. Lapollaa
N
utr Metab Cardiovasc Dis April 2015; 25(4): 418–425       http://dx.doi.org:/10.1016/j.numecd.2014.12.004

Highlights

•  Oxidative damage can generate dysfunctional HDL reducing its anti-atherogenic role.
•  Increased MetO levels in ApoA-I in patients with premature MI and in type 2 DM.
•  An increase in MetO levels in ApoA-I could result in HDL dysfunction.

 

Background and aims

ApoA-I can undergo oxidative changes that reduce anti-atherogenic role of HDL. The aim of this study was to seek any significant differences in methionine sulfoxide (MetO) content in the ApoA-I of HDL isolated from young patients with coronary heart disease (CHD), type 2 diabetics and healthy subjects.

Methods and results

We evaluated the lipid profile of 21 type 2 diabetic patients, 23 young patients with premature MI and 21 healthy volunteers; we determined in all patients the MetO content of ApoA-I in by MALDI/TOF/TOF technique. The typical MALDI spectra of the tryptic digest obtained from HDL plasma fractions all patients showed a relative abundance of peptides containing Met112O in ApoA-I in type 2 diabetic and CHD patients. This relative abundance is given as percentages of oxidized ApoA-I (OxApoA-I). OxApoA-I showed no significant correlations with lipoproteins in all patients studied, while a strong correlation emerged between the duration of diabetic disease and OxApoA-I levels in type 2 diabetic patients.

Conclusions

The most remarkable finding of our study lies in the evidence it produced of an increased HDL oxidation in patients highly susceptible to CHD. Levels of MetO residues in plasma ApoA-I, measured using an accurate, specific method, should be investigated and considered in prospective future studies to assess their role in CHD.

 

No more than 25% of the risk of coronary heart disease (CHD) can be explained by known risk factors, despite their high prevalence [1].

High-density lipoprotein (HDL) protects artery wall from atherosclerosis, in particular they remove excess cholesterol from artery wall macrophages and carries it back to the liver for excretion in bile [2]. Apolipoprotein A-I (ApoA-I) is the main protein of HDL and it plays a crucial part in the first cholesterol transport reversal step by enhancing sterol efflux from macrophages [3].

Epidemiological studies have demonstrated that plasma HDL independently predict the risk of developing atherosclerosis and cardiovascular disease [4]. More recently, however, it has emerged that HDL quality also seems to be an important parameter in atheroprotection, though there is little data in the literature to support it [5].

An increasing body of evidence shows that HDL isolated from atheromas and the plasma of patients with established CHD lacks these anti-atherogenic properties [6]. HDL can be functionally deficient in populations at high risk of CHD, as in type 2 diabetes mellitus, due to glycation and oxidative changes in their HDL, apolipoproteins, and/or enzymes[7].

ApoA-I in particular can undergo oxidative changes that reduce its anti-atherogenic role[8]. Oxidation of the Tyr and Met residues in ApoA-I by myeloperoxidase drastically impairs the protein’s ability to promote cholesterol efflux via the ABCA1 pathway [9]. Levine and colleagues [10] suggested that Met residues in protein serve as endogenous antioxidants, protecting functionally important amino acids against oxidation. In ApoA-I in particular, Met86 and Met112 are thought to be important for cholesterol efflux, and Met148is believed to be involved in LCAT activation [11].

Brock et al. recently examined the extent and sites of methionine sulfoxide (MetO) formation in the ApoA-I of HDL isolated from the plasma of healthy controls and type 1 diabetic subjects, demonstrating that MetO formation was significantly greater in diabetic patients than in a control group at all three sites considered (Met86, Met112, and Met148)[12].

Considering the relevant role of HDL oxidation in the onset of atherosclerotic processes, we ran a pilot study on a small group of type 2 diabetic patients and young people prematurely experiencing acute myocardial infarction (MI): in both these groups we found higher levels of Met112O than in healthy controls [13]. That investigation was carried out by microfluidic-LC/ESI-MS measurements. In a further study the determination of MetO content of ApoA-I in type 2 diabetic patients was performed by MALDI/MS [14] and the results obtained perfectly overlap those achieved in the previous LC/MS investigation. These results proved that possible oxidation phenomena, sometimes observed in MALDI conditions [15], are in this case absent.

The aim of this study was to assess larger study groups to seek any significant differences in MetO between patients with premature MI, type 2 diabetics and healthy subjects, and to identify any correlations with these individuals’ lipoproteins. A secondary aim was to see whether the duration of the diabetic patients’ disease correlated with HDL oxidation.

MALDI/MS

MALDI/time of flight (TOF) and MALDI/TOF/TOF measurements were performed using a MALDI/TOF/TOF UltrafleXtreme instrument (Bruker Daltonics, Bremen, Germany), equipped with a 1 kHz smartbeam II laser (λ = 355 nm) and operating in the positive reflectron ion mode. The instrumental conditions were: IS1 = 25 kV; IS2 = 21.65 kV; reflectron potential = 26.3 kV; delay time = 0 nsec. The matrix was α-cyano-4-hydroxycinnamic acid (HCCA) (saturated solution in H2O/acetonitrile (50:50; v/v) containing 0.1% TFA). Five μL of purified tryptic digest and 5 μL of matrix solution were mixed together, then 1 μL of the resulting mixture was deposited on the stainless steel sample holder and allowed to dry before placing it in the mass spectrometer. External mass calibration (Peptide Calibration Standard) was based on monoisotopic values of [M+H]+ of angiotensin II, angiotensin I, substance P, bombesin, ACTH clip [1], [2], [3], [4],[5], [6], [7], [8], [9], [10], [11], [12], [13], [14], [15], [16] and [17], ACTH clip (18–39), somatostatin 28 at m/z 1046.5420, 1296.6853, 1347.7361, 1619.8230, 2093.0868, 2465.1990 and 3147.4714. TOF/TOF experiments were performed using the LIFT device in the following experimental conditions: IS1: 7.5 kV; IS2: 6.75 kV; Lift1: 19 kV; Lift2: 3.7 kV; Reflector1: 29.5 kV; delay time: 70 ns.

Table 1 shows the demographic and clinical characteristics of patients and controls. The three groups were matched for age and smoke; the controls and diabetics were also matched for gender, while the premature MI group consisted almost entirely of men, with only one female patient. Type 2 diabetic patients were not in a situation of good metabolic control, their HbA1c levels being a mean 8.22 ± 0.84% and their FPG 156.7 ± 29.7 mg/dl.

Table 1.Clinical characteristics of type 2 diabetic patients, young patients with premature CHD and controls. Data are expressed as mean ± standard deviation. To assess statistical differences between groups, ANOVA followed by Tukey’spost-hoc test was used. ●●● p < 0.001; ●● p < 0.01; ● p < 0.05; ns: not significant;:not applied. Abbreviations: FPG = fasting plasma glucose; TC = total cholesterol; LDL = low-density lipoprotein; HDL = high-density lipoprotein; OxApoAI = oxidized Apolipoprotein AI; MI = myocardial infarction.

Control subjects (C)
(n = 21)
CHD patients (CHD)
(n = 23)
Type 2 diabetic patients (D)
(n = 21)
P


C vsCHD CvsD CHDvs D
Gender (M/F) 6/15 22/1 10/11
Age (yrs) 41.4 ± 2.8 40.7 ± 3.4 51.8 ± 3.5 ns ns ns
Diabetes duration (yrs) 8.5 ± 3.9
FPG (mg/dl) 83.5 ± 4.8 89.1 ± 7.4 156.7 ± 29.7 ns ●●● ●●●
HbA1c (%) 5.2 ± 0.2 5.3 ± 0.2 8.2 ± 0.8 ns ●●● ●●●
TC (mg/dl) 203.2 ± 33.3 205.3 ± 26.3 203.2 ± 37.0 ns ns ns
LDL (mg/dl) 117.5 ± 30.6 143.7 ± 24.7 118.3 ± 30.6 ●● ns
HDL (mg/dl) 68.7 ± 11.2 38.3 ± 10.4 49.7 ± 14.0 ●●● ●●● ●●
Triglycerides (mg/dl) 85.4 ± 21.6 146.3 ± 55.9 178.0 ± 91.8 ●● ●●● ns
ApoA1 (mg/dl) 148.2 ± 31.3 117.2 ± 14.5 128.9 ± 14.7 ns
OX ApoA1 (%) 1.7 ± 1.3 4.8 ± 2.6 10.6 ± 5.3 ●●● ●●●
MI (no/yes) 21/0 0/23 21/0
Statin therapy (yes/no) 0/21 23/0 18/3 ns
Anti-platelet agents (yes/no) 0/21 23/0 17/4 ns
Antihypertensive drugs (yes/no) 0/21 23/0 20/1 ns
Smokers (yes/no/ex) 4/15/2 5/16/2 6/14/1 ns ns ns

The three groups had similar total cholesterol levels. The group of patients with a premature MI had the highest levels of LDL cholesterol and the lowest levels of HDL cholesterol. Their triglycerides were also higher than in the healthy controls, but lower than in the diabetic patients.

Characterization of Met112 and Met112-O containing peptides

The typical MALDI spectra of the tryptic digest obtained from HDL plasma fractions of healthy subjects, diabetics and CHD patients are given in Fig. 1. MS/MS experiments performed on the two ions at m/z 1283.6 and 2645.4 showed that the sequences of the corresponding peptides are W108QEEM112ELYR and V97QPYLDDFQKKWQEEM112ELYR, both of which contain the methionine residue in position 112 (Met112). Looking at selected regions of the spectra related to the two above-mentioned ions, some differences appear between the healthy controls vs the diabetic patients and CHD patients. In the case of the diabetics and CHD patients, the two peaks at m/z 1299 and 2661 become more evident than those detected in the case of healthy subjects. These two peptides, differing from the above-described species by 16 Da, can be justified by the presence of the previously-mentioned peptides containing a Met112O moiety (see Fig. 2). MS/MS experiments performed on these two ions confirms this hypothesis, based on the presence of a fragment ion due to the loss of CH3SOH. This result confirms that oxidation occurs at Met112 in both the peptides. The above-described relative abundance of peptides containing Met112O- and Met112 was ascertained for all samples. The percentages of OxApoA-I were calculated dividing the sum of the abundances of the peaks at m/z 1299 and 2661 (originating from oxidation of Met112) to the sum of the abundances of the four peaks of interest: the results so obtained are shown in Table 1. Both the diabetic and the CHD patients showed significantly higher OxApoA-I levels than controls. We did not observe any significant correlation between the levels of ApoA-I and OxApoA-I in all groups (controls: r = −0.031; diabetics: r = 0.092; CHD patients: r = 0.20, respectively).

The typical MALDI spectra of the tryptic digest obtained from HDL plasma ...
Figure 1.

The typical MALDI spectra of the tryptic digest obtained from HDL plasma fractions of healthy subjects, diabetic and CHD patients.

Expanded view (A: m/z 1283–1299; B: m/z 2635–2690) of the MALDI mass spectra of ...
Figure 2.

Expanded view (A: m/z 1283–1299; B: m/z 2635–2690) of the MALDI mass spectra of tryptic digests from healthy subjects, diabetic patients and CHD patients.

It is to underline that the possible ex-vivo oxidation of methionine residue was checked analyzing the lyophilized HDL samples after two and four months of storage at −30 °C. No significant variation in the content of Met112O was observed, indicating that ex-vivo oxidation is inhibited at storage temperature.

Correlations

OxApoA-I showed no significant correlations with lipoproteins, while there were inverse significant correlations between HDL cholesterol and triglycerides in both the diabetic and the CHD patients (p < 0.02), but not in the healthy controls, as shown in Table 2. No correlation emerged between the OxApoA-I and HbA1c levels in the diabetic patients (r = 0.0344).

Table 2.Linear correlation between oxidized ApoA-I (Ox-ApoA-I) and serum cholesterol in the three groups of patients. Data are the Pearson product–moment correlation coefficient (Pearson’s r) with the lower and upper 95% confidence intervals (in parentheses).*p < 0.02.

Correlation between variables Control subjects, n = 21
(Lower and upper 95% C.I.)
CHD patients, n = 23
(Lower and upper 95% C.I.)
Diabetic patients, n = 21
(Lower and upper 95% C.I.)
Ox-ApoA-1 vs total cholesterol 0.3757
(−0.0669 ÷ 0.6947)
0.0519
(−0.3681 ÷ 0.4544)
−0.3287
(−0.6659 ÷ 0.1200)
Ox-ApoA-1 vs LDL-cholesterol 0.3557
(−0.0897 ÷ 0.6826)
−0.1688
(−0.5432 ÷ 0.2616)
−0.3193
(−0.6600 ÷ 0.1303)
Ox-ApoA-1 vs HDL-cholesterol 0.0745
(−0.3690 ÷ 0.4904)
0.3130
(−0.1139 ÷ 0.6423)
0.0839
(−0.3608 ÷ 0.4976)
Ox-ApoA-1vs triglycerides 0.1965
(−0.2570 ÷ 0.5790)
0.0434
(−0.3755 ÷ 0.4476)
−0.1953
(−0.5782÷0.2581)
Triglycerides vs HDL-cholesterol −0.3973
(−0.7076 ÷ 0.0415)
−0.4898*
(−0.7505 ÷ −0.0972)
−0.5413*
(−0.7887 ÷ −0.1431)

In order to evaluate with a more integrated approach the presence of interrelationships among variables, the non-parametric technique of PCA was considered. The analysis was extended to the three groups as a whole, in order to check any distribution among the individuals, and the respective role of the considered variables. As the biplot of Fig. 3shows, it was confirmed the previously found lack of any relationship between the OxApoA-I levels and HDL cholesterol or triglycerides, and it was confirmed also the presence of an inverse correlation between HDL cholesterol or triglycerides; moreover, from this analysis a strong direct correlation between the duration of diabetic disease and OxApoA-I levels emerged.

In order to evaluate with a more integrated approach the presence of interrelationships among variables, the non-parametric technique of PCA was considered. The analysis was extended to the three groups as a whole, in order to check any distribution among the individuals, and the respective role of the considered variables. As the biplot of Fig. 3shows, it was confirmed the previously found lack of any relationship between the OxApoA-I levels and HDL cholesterol or triglycerides, and it was confirmed also the presence of an inverse correlation between HDL cholesterol or triglycerides; moreover, from this analysis a strong direct correlation between the duration of diabetic disease and OxApoA-I levels emerged.

Biplot of the first two principal components (PC1 and PC2) obtained by PCA ...
Figure 3.

Biplot of the first two principal components (PC1 and PC2) obtained by PCA conducted on the most representative variables from diabetic patients, CHD patients and controls.

In the present, small cross-sectional study, our data analyses support the impression that the atheroprotective effect of HDL may be deficient in patients experiencing a premature MI and in cases of type 2 DM, both models of accelerated atherosclerosis [23]. This HDL dysfunction could be due to an increase in MetO levels in ApoA-I. We demonstrated, not only that type 2 diabetic patients and young patients with premature acute MI share the same ApoA-I oxidation, but also and more importantly they both have a greater HDL oxidation than controls, irrespective of their HDL levels. This feature was recently observed in type 1 diabetic patients compared with healthy controls, and it may contribute to an accelerated atherosclerosis [12]. These findings provide a new clinical perspective compared to preliminary results obtained by microfluidic-LC/ESI-MS [13], this time using an alternative technique (MALDI/MS), that makes the analysis far less time-consuming, as we previously showed in type 2 diabetic patients and healthy controls [14]. Our group of type 2 diabetic patients showed no signs of CHD despite their more severely oxidized HDL. We surmise that they offset the higher levels of oxidized HDL with higher levels of HDL, so the ratio of HDL to oxidized HDL might be a better marker of CHD than low HDL levels. Unfortunately, since our method only allowed for a semiquantitative assessment of the oxidation of the above-described peptides, these data cannot be used to calculate the HDL/oxidized-HDL ratio.

It is worth noting that no correlation emerged between MetO levels in ApoA-I and HbA1c, indicating that ApoA-I oxidation appears unrelated to the degree of glycemic control. This finding is in agreement with previous observations that have shown no correlation between glyco-oxidation products, such as glyoxal and methylglyoxal, which better represent the real glyco-oxidative stress experienced by patients [24].

On the other hand, our data suggest that duration of disease might be the parameter most closely related to MetO levels in ApoA-I in type 2 diabetes. In this contest, the antioxidant system could play an important part in the onset of cardiovascular complications by counter-regulating the increased oxidative stress, as we found in various phenotypes of type 2 diabetic patients with and without micro- and macrovascular complications [25] and [26]. Several studies have also demonstrated that decreased levels of antioxidants favor cardiovascular disease in subjects without diabetes [27]. As regards our data on HDL oxidation, we hypothesized that the increase of Apo-AI oxidation could be due to the decreased levels of antioxidant defenses that characterized type 2 diabetic patients with long duration of disease and patient with premature MI. Recent observations, in fact, showed that serum myeloperoxidase/paraoxonase 1 ratio is a potential indicator of dysfunctional HDL and risk stratification in CHD [28]. At the end HDL oxidation process could be partially independent from oxidative stress burden, but affected by decreased antioxidant capacity.

As for the higher triglyceride levels found in our type 2 DM and CHD patients, we surmise that hypertriglyceridemia could be a prognostic marker even in young patients with premature MI, irrespective of other cardiovascular risk factors, as previously reported[29]. Both our groups of patients showed a strong inverse relationship between their HDL and triglyceride levels, a situation typical of insulin resistance and found associated with MI occurring before 40 years of age [30].

As regards LDL cholesterol, we found the highest level in young CHD patients who were all in statin therapy. Considering the very short period of statin therapy and knowing that to reach the full effect it needs at still a month, CHD patients showed LDL cholesterol levels not still at target. On the other side, statin therapy hardly have had an impact on the oxidation of HDL. In any case statin protective effect on the oxidation strengthen our conclusions.

All these quantitative and qualitative lipoprotein features (higher oxidized HDL, higher triglycerides and lower HDL levels) suggest the feasibility of characterizing patients at high risk of CHD in terms of their lipid profile, as illustrated in the integrated biplot ofFig. 3.

In conclusion, the most remarkable finding of our study lies in the evidence it produced of an increased HDL oxidation in patients highly susceptible to CHD. Levels of MetO residues in plasma ApoA-I, measured using an accurate, specific method, should be investigated and considered in prospective future studies in order to assess their possible role as a novel risk factor – and eventually as a therapeutic target – to reduce the burden of cardiovascular complications.

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Glucokinase target for type 2 diabetes

Larry H. Bernstein, MD, FCAP, Curator

LPBI

 

 

Pfizer’s PF 04991532 a Hepatoselective Glucokinase Activator Clinical Candidate for Treating Type 2 Diabetes Mellitus
DR ANTHONY MELVIN CRASTO, WORLD DRUG TRACKER
http://newdrugapprovals.org/2015/11/27/pfizers-pf-04991532-a-hepatoselective-glucokinase-activator-clinical-candidate-for-treating-type-2-diabetes-mellitus/

 

PF 04991532

GKA PF-04991532

(S)-6-{3-cyclopentyl-2-[4-(trifluoromethyl)-1H-imidazol-1-yl]propanamido}nicotinic acid

(S)-6-(3-Cyclopentyl-2-(4-(trifluoromethyl)-1H-imidazol-1-yl)propanamido)nicotinic Acid

(S)-6-(3-cyclopentyl-2-(4-(trifluoromethyl)-1H-imidazol-1-yl)propanamido)nicotinic acid

MW 396.36, MF C18 H19 F3 N4 O3

CAS 1215197-37-7

3-​Pyridinecarboxylic acid, 6-​[[(2S)​-​3-​cyclopentyl-​1-​oxo-​2-​[4-​(trifluoromethyl)​-​1H-​imidazol-​1-​yl]​propyl]​amino]​-

http://www.biochemj.org/content/441/3/881

 

Type 2 diabetes mellitus (T2DM) is a rapidly expanding public epidemic affecting over 300 million people worldwide. This disease is characterized by elevated fasting plasma glucose (FPG), insulin resistance, abnormally elevated hepatic glucose production (HGP), and reduced glucose-stimulated insulin secretion (GSIS). Moreover, long-term lack of glycemic control increases risk of complications from neuropathic, microvascular, and macrovascular diseases.

The standard of care for T2DM is metformin followed by sulfonylureas, dipeptidyl peptidase-4 (DPP-IV) inhibitors, and thiazolidinediones (TZD) as second line oral therapies. As disease progression continues, patients typically require injectable agents such as glucagon-like peptide-1 (GLP-1) analogues and, ultimately, insulin to help maintain glycemic control. Despite these current therapies, many patients still remain unable to safely achieve and maintain tight glycemic control, placing them at risk of diabetic complications and highlighting the need for novel therapeutic options.

 

Glucokinase (hexokinase IV) continues to be a compelling target for the treatment of type 2 diabetes given the wealth of supporting human genetics data and numerous reports of robust clinical glucose lowering in patients treated with small molecule allosteric activators. Recent work has demonstrated the ability of hepatoselective activators to deliver glucose lowering efficacy with minimal risk of hypoglycemia.

While orally administered agents require a considerable degree of passive permeability to promote suitable exposures, there is no such restriction on intravenously delivered drugs. Therefore, minimization of membrane diffusion in the context of an intravenously agent should ensure optimal hepatic targeting and therapeutic index.

 

Diabetes is a major public health concern because of its increasing prevalence and associated health risks. The disease is characterized by metabolic defects in the production and utilization of carbohydrates which result in the failure to maintain appropriate blood glucose levels. Two major forms of diabetes are recognized. Type I diabetes, or insulin-dependent diabetes mellitus (IDDM), is the result of an absolute deficiency of insulin. Type II diabetes, or non-insulin dependent diabetes mellitus (NIDDM), often occurs with normal, or even elevated levels of insulin and appears to be the result of the inability of tissues and cells to respond appropriately to insulin. Aggressive control of NIDDM with medication is essential; otherwise it can progress into IDDM.

As blood glucose increases, it is transported into pancreatic beta cells via a glucose transporter. Intracellular mammalian glucokinase (GK) senses the rise in glucose and activates cellular glycolysis, i.e. the conversion of glucose to glucose-6-phosphate, and subsequent insulin release. Glucokinase is found principally in pancreatic β-cells and liver parenchymal cells. Because transfer of glucose from the blood into muscle and fatty tissue is insulin dependent, diabetics lack the ability to utilize glucose adequately which leads to undesired accumulation of blood glucose (hyperglycemia). Chronic hyperglycemia leads to decreases in insulin secretion and contributes to increased insulin resistance. Glucokinase also acts as a sensor in hepatic parenchymal cells which induces glycogen synthesis, thus preventing the release of glucose into the blood. The GK processes are thus critical for the maintenance of whole body glucose homeostasis.

It is expected that an agent that activates cellular GK will facilitate glucose-dependent secretion from pancreatic beta cells, correct postprandial hyperglycemia, increase hepatic glucose utilization and potentially inhibit hepatic glucose release. Consequently, a GK activator may provide therapeutic treatment for NIDDM and associated complications, inter alia, hyperglycemia, dyslipidemia, insulin resistance syndrome, hyperinsulinemia, hypertension, and obesity.

Several drugs in five major categories, each acting by different mechanisms, are available for treating hyperglycemia and subsequently, NIDDM (Moller, D. E., “New drug targets for Type II diabetes and the metabolic syndrome” Nature414; 821-827, (2001)): (A) Insulin secretogogues, including sulphonyl-ureas (e.g., glipizide, glimepiride, glyburide) and meglitinides (e.g., nateglidine and repaglinide) enhance secretion of insulin by acting on the pancreatic beta-cells. While this therapy can decrease blood glucose level, it has limited efficacy and tolerability, causes weight gain and often induces hypoglycemia. (B) Biguanides (e.g., metformin) are thought to act primarily by decreasing hepatic glucose production. Biguanides often cause gastrointestinal disturbances and lactic acidosis, further limiting their use. (C) Inhibitors of alpha-glucosidase (e.g., acarbose) decrease intestinal glucose absorption. These agents often cause gastrointestinal disturbances. (D) Thiazolidinediones (e.g., pioglitazone, rosiglitazone) act on a specific receptor (peroxisome proliferator-activated receptor-gamma) in the liver, muscle and fat tissues. They regulate lipid metabolism subsequently enhancing the response of these tissues to the actions of insulin. Frequent use of these drugs may lead to weight gain and may induce edema and anemia. (E) Insulin is used in more severe cases, either alone or in combination with the above agents.

Ideally, an effective new treatment for NIDDM would meet the following criteria: (a) it would not have significant side effects including induction of hypoglycemia; (b) it would not cause weight gain; (c) it would at least partially replace insulin by acting via mechanism(s) that are independent from the actions of insulin; (d) it would desirably be metabolically stable to allow less frequent usage; and (e) it would be usable in combination with tolerable amounts of any of the categories of drugs listed herein.

Substituted heteroaryls, particularly pyridones, have been implicated in mediating GK and may play a significant role in the treatment of NIDDM. For example, U.S. Patent publication No. 2006/0058353 and PCT publication Nos. WO2007/043638, WO2007/043638, and WO2007/117995 recite certain heterocyclic derivatives with utility for the treatment of diabetes. Although investigations are on-going, there still exists a need for a more effective and safe therapeutic treatment for diabetes, particularly NIDDM.

 

s1

s1

 

s1

 

PATENT

US 20100063063

http://www.google.com/patents/US20100063063

SYNTHESIS CONSTRUCTION

6-aminonicotinic acid

 

BENZYL BROMIDE

 

Figure US20100063063A1-20100311-C00076

FIRST KEY INTERMEDIATE

 

SECOND SERIES FOR NEXT INTERMEDIATE

CONDENSED WITH

4-Trifluoromethyl-1H-imidazole

TO  GIVE PRODUCT SHOWN BELOW

 

Figure US20100063063A1-20100311-C00025

(S)-methyl 3-cyclopentyl-2-(4-(trifluoromethyl)-1H-imidazol-1-yl)propanoate (I-8a)

 

CONVERTED TO ACID CHLORIDE, (S)-3-cyclopentyl-2-(4-(trifluoromethyl)-1H-imidazol-1-yl)propanoyl chloride (I-8c)

AND CONDENSED WITH

Figure US20100063063A1-20100311-C00076

WILL GIVE BENZYL DERIVATIVE

THEN DEBENZYLATION TO FINAL PRODUCT

 

 

 

1H NMR (400 MHz, DMSO-d6) δ 13.10-13.25 (1H), 11.44 (1H), 8.83 (1H), 8.23-8.26 (1H), 8.09-8.12 (1H), 7.94-7.95 (2H), 5.22-5.26 (1H), 2.06-2.17 (2H), 1.29-1.64 (8H), 1.04-1.07 (1H); m/z 397.3 (M+H)+.

 

Organic Process Research & Development (2012), 16(10), 1635-1645

http://pubs.acs.org/doi/abs/10.1021/op300194c

Abstract Image

This work describes the process development and manufacture of early-stage clinical supplies of a hepatoselective glucokinase activator, a potential therapy for type 2 diabetes mellitus. Critical issues centered on challenges associated with the synthesis of intermediates and API bearing a particularly racemization-prone α-aryl carboxylate functionality. In particular, a T3P-mediated amidation process was optimized for the coupling of a racemization-prone acid substrate and a relatively non-nucleophilic amine. Furthermore, an unusually hydrolytically-labile amide in the API also complicated the synthesis and isolation of drug substance. The evolution of the process over multiple campaigns is presented, resulting in the preparation of over 110 kg of glucokinase activator.

(S)-6-(3-Cyclopentyl-2-(4-(trifluoromethyl)-1H-imidazol-1-yl)propanamido)nicotinic Acid (1)

 

Journal of Medicinal Chemistry (2012), 55(3), 1318-1333

http://pubs.acs.org/doi/abs/10.1021/jm2014887

Abstract Image

Glucokinase is a key regulator of glucose homeostasis, and small molecule allosteric activators of this enzyme represent a promising opportunity for the treatment of type 2 diabetes. Systemically acting glucokinase activators (liver and pancreas) have been reported to be efficacious but in many cases present hypoglycaemia risk due to activation of the enzyme at low glucose levels in the pancreas, leading to inappropriately excessive insulin secretion. It was therefore postulated that a liver selective activator may offer effective glycemic control with reduced hypoglycemia risk. Herein, we report structure–activity studies on a carboxylic acid containing series of glucokinase activators with preferential activity in hepatocytes versus pancreatic β-cells. These activators were designed to have low passive permeability thereby minimizing distribution into extrahepatic tissues; concurrently, they were also optimized as substrates for active liver uptake via members of the organic anion transporting polypeptide (OATP) family. These studies lead to the identification of 19 as a potent glucokinase activator with a greater than 50-fold liver-to-pancreas ratio of tissue distribution in rodent and non-rodent species. In preclinical diabetic animals, 19 was found to robustly lower fasting and postprandial glucose with no hypoglycemia, leading to its selection as a clinical development candidate for treating type 2 diabetes.

Bioorganic & Medicinal Chemistry Letters (2013), 23(24), 6588-6592

http://www.sciencedirect.com/science/article/pii/S0960894X13012638

Image for unlabelled figure

 

Structure of Hepatoselective GKA PF-04991532 (1).

Figure 1.

Structure of Hepatoselective GKA PF-04991532 (1).

 

Pfizer’s PF 04937319 glucokinase activators for the treatment of Type 2 diabetes
DR ANTHONY MELVIN CRASTO, WORLD DRUG TRACKER
http://newdrugapprovals.org/2015/11/27/pfizers-pf-04937319-glucokinase-activators-for-the-treatment-of-type-2-diabetes/

Graphical abstract: Designing glucokinase activators with reduced hypoglycemia risk: discovery of N,N-dimethyl-5-(2-methyl-6-((5-methylpyrazin-2-yl)-carbamoyl)benzofuran-4-yloxy)pyrimidine-2-carboxamide as a clinical candidate for the treatment of type 2 diabetes mellitus

PF 04937319

N,N-dimethyl-5-(2-methyl-6-((5-methylpyrazin-2-yl)-carbamoyl)benzofuran-4-yloxy)pyrimidine-2-carboxamide

MW 432.43

MF C22 H20 N6 O4
CAS 1245603-92-2
2-​Pyrimidinecarboxamid​e, N,​N-​dimethyl-​5-​[[2-​methyl-​6-​[[(5-​methyl-​2-​pyrazinyl)​amino]​carbonyl]​-​4-​benzofuranyl]​oxy]​-
N,N-Dimethyl-5-(2-methyl-6-((5-methylpyrazin-2-yl)carbamoyl)-benzofuran-4- yloxy)pyrimidine-2-carboxamide
Pfizer Inc. clinical candidate currently in Phase 2 development.
CLINICAL TRIALS

A trial to assess the safety, tolerability, pharmacokinetics, and pharmacodynamics of single doses of PF-04937319 in subjects with type 2 diabetes mellitus (NCT01044537)

Multiple dose study of PF-04937319 in patients with type 2 diabetes (NCT01272804)
Phase 2 study to evaluate safety and efficacy of investigational drug – PF04937319 in patients with type 2 diabetes (NCT01475461)

 

SYNTHESIS

PF 319 SYN

Glucokinase is a key regulator of glucose homeostasis and small molecule activators of this enzyme represent a promising opportunity for the treatment of Type 2 diabetes. Several glucokinase activators have advanced to clinical studies and demonstrated promising efficacy; however, many of these early candidates also revealed hypoglycemia as a key risk. In an effort to mitigate this hypoglycemia risk while maintaining the promising efficacy of this mechanism, we have investigated a series of substituted 2-methylbenzofurans as “partial activators” of the glucokinase enzyme leading to the identification ofN,N-dimethyl-5-(2-methyl-6-((5-methylpyrazin-2-yl)-carbamoyl)benzofuran-4-yloxy)pyrimidine-2-carboxamide as an early development candidate.

 

It is expected that an agent that activates cellular GK will facilitate glucose-dependent secretion from pancreatic beta cells, correct postprandial hyperglycemia, increase hepatic glucose utilization and potentially inhibit hepatic glucose release. Consequently, a GK activator may provide therapeutic treatment for NIDDM and associated complications, inter alia, hyperglycemia, dyslipidemia, insulin resistance syndrome, hyperinsulinemia, hypertension, and obesity. Several drugs in five major categories, each acting by different mechanisms, are available for treating hyperglycemia and subsequently, NIDDM (Moller, D. E., “New drug targets for Type 2 diabetes and the metabolic syndrome” Nature 414; 821 -827, (2001 )): (A) Insulin secretogogues, including sulphonyl-ureas (e.g., glipizide, glimepiride, glyburide) and meglitinides (e.g., nateglidine and repaglinide) enhance secretion of insulin by acting on the pancreatic beta-cells. While this therapy can decrease blood glucose level, it has limited efficacy and tolerability, causes weight gain and often induces hypoglycemia. (B) Biguanides (e.g., metformin) are thought to act primarily by decreasing hepatic glucose production. Biguanides often cause gastrointestinal disturbances and lactic acidosis, further limiting their use. (C) Inhibitors of alpha-glucosidase (e.g., acarbose) decrease intestinal glucose absorption. These agents often cause gastrointestinal disturbances. (D) Thiazolidinediones (e.g., pioglitazone, rosiglitazone) act on a specific receptor (peroxisome proliferator-activated receptor-gamma) in the liver, muscle and fat tissues. They regulate lipid metabolism subsequently enhancing the response of these tissues to the actions of insulin. Frequent use of these drugs may lead to weight gain and may induce edema and anemia. (E) Insulin is used in more severe cases, either alone or in combination with the above agents. Ideally, an effective new treatment for NIDDM would meet the following criteria: (a) it would not have significant side effects including induction of hypoglycemia; (b) it would not cause weight gain; (c) it would at least partially replace insulin by acting via mechanism(s) that are independent from the actions of insulin; (d) it would desirably be metabolically stable to allow less frequent usage; and (e) it would be usable in combination with tolerable amounts of any of the categories of drugs listed herein.

Substituted heteroaryls, particularly pyridones, have been implicated in mediating GK and may play a significant role in the treatment of NIDDM. For example, U.S. Patent publication No. 2006/0058353 and PCT publication No’s. WO2007/043638, WO2007/043638, and WO2007/117995 recite certain heterocyclic derivatives with utility for the treatment of diabetes. Although investigations are on-going, there still exists a need for a more effective and safe therapeutic treatment for diabetes, particularly NIDDM.

 

Designing glucokinase activators with reduced hypoglycemia risk: discovery of N,N-dimethyl-5-(2-methyl-6-((5-methylpyrazin-2-yl)-carbamoyl)benzofuran-4-yloxy)pyrimidine-2-carboxamide as a clinical candidate for the treatment of type 2 diabetes mellitus

*Corresponding authors
aPfizer Worldwide Research & Development, Eastern Point Road, Groton
E-mail: jeffrey.a.pfefferkorn@pfizer.com
Tel: +860 686 3421
Med. Chem. Commun., 2011,2, 828-839

DOI: 10.1039/C1MD00116G

http://pubs.rsc.org/en/content/articlelanding/2011/md/c1md00116g/unauth#!divAbstract

http://www.rsc.org/suppdata/md/c1/c1md00116g/c1md00116g.pdf

Glucokinase is a key regulator of glucose homeostasis and small molecule activators of this enzyme represent a promising opportunity for the treatment of Type 2 diabetes. Several glucokinase activators have advanced to clinical studies and demonstrated promising efficacy; however, many of these early candidates also revealed hypoglycemia as a key risk. In an effort to mitigate this hypoglycemia risk while maintaining the promising efficacy of this mechanism, we have investigated a series of substituted 2-methylbenzofurans as “partial activators” of the glucokinase enzyme leading to the identification ofN,N-dimethyl-5-(2-methyl-6-((5-methylpyrazin-2-yl)-carbamoyl)benzofuran-4-yloxy)pyrimidine-2-carboxamide as an early development candidate.

Graphical abstract: Designing glucokinase activators with reduced hypoglycemia risk: discovery of N,N-dimethyl-5-(2-methyl-6-((5-methylpyrazin-2-yl)-carbamoyl)benzofuran-4-yloxy)pyrimidine-2-carboxamide as a clinical candidate for the treatment of type 2 diabetes mellitus

N,N-Dimethyl-5-(2-methyl-6-((5-methylpyrazin-2-yl)carbamoyl)-benzofuran-4- yloxy)pyrimidine-2-carboxamide (28).

 

PAPER

 

http://pubs.rsc.org/en/content/articlelanding/2013/md/c2md20317k#!divAbstract

 

PAPER

Bioorganic & Medicinal Chemistry Letters (2013), 23(16), 4571-4578

http://www.sciencedirect.com/science/article/pii/S0960894X13007452

Glucokinase activators 1 and 2.

Figure 1.

Glucokinase activators 1 and 2.

 

PATENT

Pfizer Inc.

WO 2010103437

https://www.google.co.in/patents/WO2010103437A1?cl=en

Scheme I outlines the general procedures one could use to provide compounds of the present invention having Formula (I).

Figure imgf000011_0001
PF 319 SYN

Preparations of Starting Materials and Key Intermediates

 

 

Beebe, D.A.; Ross, T.T.; Rolph, T.P.; Pfefferkorn, J.A.; Esler, W.P.
The glucokinase activator PF-04937319 improves glycemic control in combination with exercise without causing hypoglycemia in diabetic rats
74th Annu Meet Sci Sess Am Diabetes Assoc (ADA) (June 13-17, San Francisco) 2014, Abst 1113-P

 

Amin, N.B.; Aggarwal, N.; Pall, D.; Paragh, G.; Denney, W.S.; Le, V.; Riggs, M.; Calle, R.A.
Two dose-ranging studies with PF-04937319, a systemic partial activator of glucokinase, as add-on therapy to metformin in adults with type 2 diabetes
Diabetes Obes Metab 2015, 17(8): 751

 

Study to compare single dose of three modified release formulations of PF-04937319 with immediate release material-sparing-tablet (IR MST) formulation previously studied in adults with type 2 diabetes mellitus (NCT02206607)

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Biochemistry and Dysmetabolism of Aging and Serious Illness, Volume 2 (Volume Two: Latest in Genomics Methodologies for Therapeutics: Gene Editing, NGS and BioInformatics, Simulations and the Genome Ontology), Part 1: Next Generation Sequencing (NGS)

Biochemistry and Dysmetabolism of Aging and Serious Illness

Curator: Larry H. Bernstein, MD, FCAP

 

White Matter Lipids as a Ketogenic Fuel Supply in Aging Female Brain: Implications for Alzheimer’s Disease

Lauren P. Klosinski, Jia Yao, Fei Yin, Alfred N. Fonteh, Michael G. Harrington, Trace A. Christensen, Eugenia Trushina, Roberta Diaz Brinton
http://www.ebiomedicine.com/article/S2352-3964(15)30192-4/abstract      DOI: http://dx.doi.org/10.1016/j.ebiom.2015.11.002
Highlights
  • Mitochondrial dysfunction activates mechanisms for catabolism of myelin lipids to generate ketone bodies for ATP production.
  • Mechanisms leading to ketone body driven energy production in brain coincide with stages of reproductive aging in females.
  • Sequential activation of myelin catabolism pathway during aging provides multiple therapeutic targets and windows of efficacy.

The mechanisms underlying white matter degeneration, a hallmark of multiple neurodegenerative diseases including Alzheimer’s, remain unclear. Herein we provide a mechanistic pathway, spanning multiple transitions of aging, that links mitochondrial dysfunction early in aging with later age white matter degeneration. Catabolism of myelin lipids to generate ketone bodies can be viewed as an adaptive survival response to address brain fuel and energy demand. Women are at greatest risk of late-onset-AD, thus, our analyses in female brain address mechanisms of AD pathology and therapeutic targets to prevent, delay and treat AD in the sex most affected with potential relevance to men.

 

White matter degeneration is a pathological hallmark of neurodegenerative diseases including Alzheimer’s. Age remains the greatest risk factor for Alzheimer’s and the prevalence of age-related late onset Alzheimer’s is greatest in females. We investigated mechanisms underlying white matter degeneration in an animal model consistent with the sex at greatest Alzheimer’s risk. Results of these analyses demonstrated decline in mitochondrial respiration, increased mitochondrial hydrogen peroxide production and cytosolic-phospholipase-A2 sphingomyelinase pathway activation during female brain aging. Electron microscopic and lipidomic analyses confirmed myelin degeneration. An increase in fatty acids and mitochondrial fatty acid metabolism machinery was coincident with a rise in brain ketone bodies and decline in plasma ketone bodies. This mechanistic pathway and its chronologically phased activation, links mitochondrial dysfunction early in aging with later age development of white matter degeneration. The catabolism of myelin lipids to generate ketone bodies can be viewed as a systems level adaptive response to address brain fuel and energy demand. Elucidation of the initiating factors and the mechanistic pathway leading to white matter catabolism in the aging female brain provides potential therapeutic targets to prevent and treat demyelinating diseases such as Alzheimer’s and multiple sclerosis. Targeting stages of disease and associated mechanisms will be critical.

3. Results

  1. 3.1. Pathway of Mitochondrial Deficits, H2O2 Production and cPLA2 Activation in the Aging Female Brain
  2. 3.2. cPLA2-sphingomyelinase Pathway Activation in White Matter Astrocytes During Reproductive Senescence
  3. 3.3. Investigation of White Matter Gene Expression Profile During Reproductive Senescence
  4. 3.4. Ultra Structural Analysis of Myelin Sheath During Reproductive Senescence
  5. 3.5. Analysis of the Lipid Profile of Brain During the Transition to Reproductive Senescence
  6. 3.6. Fatty Acid Metabolism and Ketone Generation Following the Transition to Reproductive Senescence

 

4. Discussion

Age remains the greatest risk factor for developing AD (Hansson et al., 2006, Alzheimer’s, 2015). Thus, investigation of transitions in the aging brain is a reasoned strategy for elucidating mechanisms and pathways of vulnerability for developing AD. Aging, while typically perceived as a linear process, is likely composed of dynamic transition states, which can protect against or exacerbate vulnerability to AD (Brinton et al., 2015). An aging transition unique to the female is the perimenopausal to menopausal conversion (Brinton et al., 2015). The bioenergetic similarities between the menopausal transition in women and the early appearance of hypometabolism in persons at risk for AD make the aging female a rational model to investigate mechanisms underlying risk of late onset AD.

Findings from this study replicate our earlier findings that age of reproductive senescence is associated with decline in mitochondrial respiration, increased H2O2 production and shift to ketogenic metabolism in brain (Yao et al., 2010, Ding et al., 2013, Yin et al., 2015). These well established early age-related changes in mitochondrial function and shift to ketone body utilization in brain, are now linked to a mechanistic pathway that connects early decline in mitochondrial respiration and H2O2 production to activation of the cPLA2-sphingomyelinase pathway to catabolize myelin lipids resulting in WM degeneration (Fig. 12). These lipids are sequestered in lipid droplets for subsequent use as a local source of ketone body generation via astrocyte mediated beta-oxidation of fatty acids. Astrocyte derived ketone bodies can then be transported to neurons where they undergo ketolysis to generate acetyl-CoA for TCA derived ATP generation required for synaptic and cell function (Fig. 12).

Thumbnail image of Fig. 12. Opens large image

http://www.ebiomedicine.com/cms/attachment/2040395791/2053874721/gr12.sml

Fig. 12

Schematic model of mitochondrial H2O2 activation of cPLA2-sphingomyelinase pathway as an adaptive response to provide myelin derived fatty acids as a substrate for ketone body generation: The cPLA2-sphingomyelinase pathway is proposed as a mechanistic pathway that links an early event, mitochondrial dysfunction and H2O2, in the prodromal/preclinical phase of Alzheimer’s with later stage development of pathology, white matter degeneration. Our findings demonstrate that an age dependent deficit in mitochondrial respiration and a concomitant rise in oxidative stress activate an adaptive cPLA2-sphingomyelinase pathway to provide myelin derived fatty acids as a substrate for ketone body generation to fuel an energetically compromised brain.

Biochemical evidence obtained from isolated whole brain mitochondria confirms that during reproductive senescence and in response to estrogen deprivation brain mitochondria decline in respiratory capacity (Yao et al., 2009, Yao et al., 2010, Brinton, 2008a, Brinton, 2008b, Swerdlow and Khan, 2009). A well-documented consequence of mitochondrial dysfunction is increased production of reactive oxygen species (ROS), specifically H2O2 (Boveris and Chance, 1973, Beal, 2005, Yin et al., 2014, Yap et al., 2009). While most research focuses on the damage generated by free radicals, in this case H2O2 functions as a signaling molecule to activate cPLA2, the initiating enzyme in the cPLA2-sphingomyelinase pathway (Farooqui and Horrocks, 2006, Han et al., 2003, Sun et al., 2004). In AD brain, increased cPLA2 immunoreactivity is detected almost exclusively in astrocytes suggesting that activation of the cPLA2-sphingomyelinase pathway is localized to astrocytes in AD, as opposed to the neuronal or oligodendroglial localization that is observed during apoptosis (Sun et al., 2004, Malaplate-Armand et al., 2006, Di Paolo and Kim, 2011, Stephenson et al., 1996,Stephenson et al., 1999). In our analysis, cPLA2 (Sanchez-Mejia and Mucke, 2010) activation followed the age-dependent rise in H2O2 production and was sustained at an elevated level.

Direct and robust activation of astrocytic cPLA2 by physiologically relevant concentrations of H2O2 was confirmed in vitro. Astrocytic involvement in the cPLA2-sphingomyelinase pathway was also indicated by an increase in cPLA2 positive astrocyte reactivity in WM tracts of reproductively incompetent mice. These data are consistent with findings from brains of persons with AD that demonstrate the same striking localization of cPLA2immunoreactivity within astrocytes, specifically in the hippocampal formation (Farooqui and Horrocks, 2004). While neurons and astrocytes contain endogenous levels of cPLA2, neuronal cPLA2 is activated by an influx of intracellular calcium, whereas astrocytic cPLA2 is directly activated by excessive generation of H2O2 (Sun et al., 2004, Xu et al., 2003, Tournier et al., 1997). Evidence of this cell type specific activation was confirmed by the activation of cPLA2 in astrocytes by H2O2 and the lack of activation in neurons. These data support that astrocytic, not neuronal, cPLA2 is the cellular mediator of the H2O2 dependent cPLA2-sphingomyelinase pathway activation and provide associative evidence supporting a role of astrocytic mitochondrial H2O2 in age-related WM catabolism.

The pattern of gene expression during the shift to reproductive senescence in the female mouse hippocampus recapitulates key observations in human AD brain tissue, specifically elevation in cPLA2, sphingomyelinase and ceramidase (Schaeffer et al., 2010, He et al., 2010, Li et al., 2014). Further, up-regulation of myelin synthesis, lipid metabolism and inflammatory genes in reproductively incompetent female mice is consistent with the gene expression pattern previously reported from aged male rodent hippocampus, aged female non-human primate hippocampus and human AD hippocampus (Blalock et al., 2003, Blalock et al., 2004, Blalock et al., 2010, Blalock et al., 2011, Kadish et al., 2009, Rowe et al., 2007). In these analyses of gene expression in aged male rodent hippocampus, aged female non-human primate hippocampus and human AD hippocampus down regulation of genes related to mitochondrial function, and up-regulation in multiple genes encoding for enzymes involved in ketone body metabolism occurred (Blalock et al., 2003, Blalock et al., 2004, Blalock et al., 2010, Blalock et al., 2011, Kadish et al., 2009, Rowe et al., 2007). The comparability across data derived from aging female mouse hippocampus reported herein and those derived from male rodent brain, female nonhuman brain and human AD brain strongly suggest that cPLA2-sphingomyelinase pathway activation, myelin sheath degeneration and fatty acid metabolism leading to ketone body generation is a metabolic adaptation that is generalizable across these naturally aging models and are evident in aged human AD brain. Collectively, these data support the translational relevance of findings reported herein.

Data obtained via immunohistochemistry, electron microscopy and MBP protein analyses demonstrated an age-related loss in myelin sheath integrity. Evidence for a loss of myelin structural integrity emerged in reproductively incompetent mice following activation of the cPLA2-sphingomyelinase pathway. The unraveling myelin phenotype observed following reproductive senescence and aging reported herein is consistent with the degenerative phenotype that emerges following exposure to the chemotherapy drug bortezomib which induces mitochondrial dysfunction and increased ROS generation (Carozzi et al., 2010, Cavaletti et al., 2007,Ling et al., 2003). In parallel to the decline in myelin integrity, lipid droplet density increased. In aged mice, accumulation of lipid droplets declined in parallel to the rise in ketone bodies consistent with the utilization of myelin-derived fatty acids to generate ketone bodies. Due to the sequential relationship between WM degeneration and lipid droplet formation, we posit that lipid droplets serve as a temporary storage site for myelin-derived fatty acids prior to undergoing β-oxidation in astrocytes to generate ketone bodies.

Microstructural alterations in myelin integrity were associated with alterations in the lipid profile of brain, indicative of WM degeneration resulting in release of myelin lipids. Sphingomyelin and galactocerebroside are two main lipids that compose the myelin sheath (Baumann and Pham-Dinh, 2001). Ceramide is common to both galactocerebroside and sphingomyelin and is composed of sphingosine coupled to a fatty acid. Ceramide levels increase in aging, in states of ketosis and in neurodegeneration (Filippov et al., 2012, Blazquez et al., 1999, Costantini et al., 2005). Specifically, ceramide levels are elevated at the earliest clinically recognizable stage of AD, indicating a degree of WM degeneration early in disease progression (Di Paolo and Kim, 2011,Han et al., 2002, Costantini et al., 2005). Sphingosine is statistically significantly elevated in the brains of AD patients compared to healthy controls; a rise that was significantly correlated with acid sphingomyelinase activity, Aβ levels and tau hyperphosphorylation (He et al., 2010). In our analyses, a rise in ceramides was first observed early in the aging process in reproductively incompetent mice. The rise in ceramides was coincident with the emergence of loss of myelin integrity consistent with the release of myelin ceramides from sphingomyelin via sphingomyelinase activation. Following the rise in ceramides, sphingosine and fatty acid levels increased. The temporal sequence of the lipid profile was consistent with gene expression indicating activation of ceramidase for catabolism of ceramide into sphingosine and fatty acid during reproductive senescence. Once released from ceramide, fatty acids can be transported into the mitochondrial matrix of astrocytes via CPT-1, where β-oxidation of fatty acids leads to the generation of acetyl-CoA (Glatz et al., 2010). It is well documented that acetyl-CoA cannot cross the inner mitochondrial membrane, thus posing a barrier to direct transport of acetyl-CoA generated by β-oxidation into neurons. In response, the newly generated acetyl-CoA undergoes ketogenesis to generate ketone bodies to fuel energy demands of neurons (Morris, 2005,Guzman and Blazquez, 2004, Stacpoole, 2012). Because astrocytes serve as the primary location of β-oxidation in brain they are critical to maintaining neuronal metabolic viability during periods of reduced glucose utilization (Panov et al., 2014, Ebert et al., 2003, Guzman and Blazquez, 2004).

Once fatty acids are released from myelin ceramides, they are transported into astrocytic mitochondria by CPT1 to undergo β-oxidation. The mitochondrial trifunctional protein HADHA catalyzes the last three steps of mitochondrial β-oxidation of long chain fatty acids, while mitochondrial ABAD (aka SCHAD—short chain fatty acid dehydrogenase) metabolizes short chain fatty acids. Concurrent with the release of myelin fatty acids in aged female mice, CPT1, HADHA and ABAD protein expression as well as ketone body generation increased significantly. These findings indicate that astrocytes play a pivotal role in the response to bioenergetic crisis in brain to activate an adaptive compensatory system that activates catabolism of myelin lipids and the metabolism of those lipids into fatty acids to generate ketone bodies necessary to fuel neuronal demand for acetyl-CoA and ATP.

Collectively, these findings provide a mechanistic pathway that links mitochondrial dysfunction and H2O2generation in brain early in the aging process to later stage white matter degeneration. Astrocytes play a pivotal role in providing a mechanistic strategy to address the bioenergetic demand of neurons in the aging female brain. While this pathway is coincident with reproductive aging in the female brain, it is likely to have mechanistic translatability to the aging male brain. Further, the mechanistic link between bioenergetic decline and WM degeneration has potential relevance to other neurological diseases involving white matter in which postmenopausal women are at greater risk, such as multiple sclerosis. The mechanistic pathway reported herein spans time and is characterized by a progression of early adaptive changes in the bioenergetic system of the brain leading to WM degeneration and ketone body production. Translationally, effective therapeutics to prevent, delay and treat WM degeneration during aging and Alzheimer’s disease will need to specifically target stages within the mechanistic pathway described herein. The fundamental initiating event is a bioenergetic switch from being a glucose dependent brain to a glucose and ketone body dependent brain. It remains to be determined whether it is possible to prevent conversion to or reversal of a ketone dependent brain. Effective therapeutic strategies to intervene in this process require biomarkers of bioenergetic phenotype of the brain and stage of mechanistic progression. The mechanistic pathway reported herein may have relevance to other age-related neurodegenerative diseases characterized by white matter degeneration such as multiple sclerosis.

Blood. 2015 Oct 15;126(16):1925-9.    http://dx.doi.org:/10.1182/blood-2014-12-617498. Epub 2015 Aug 14.
Targeting the leukemia cell metabolism by the CPT1a inhibition: functional preclinical effects in leukemias.
Cancer cells are characterized by perturbations of their metabolic processes. Recent observations demonstrated that the fatty acid oxidation (FAO) pathway may represent an alternative carbon source for anabolic processes in different tumors, therefore appearing particularly promising for therapeutic purposes. Because the carnitine palmitoyl transferase 1a (CPT1a) is a protein that catalyzes the rate-limiting step of FAO, here we investigated the in vitro antileukemic activity of the novel CPT1a inhibitor ST1326 on leukemia cell lines and primary cells obtained from patients with hematologic malignancies. By real-time metabolic analysis, we documented that ST1326 inhibited FAO in leukemia cell lines associated with a dose- and time-dependent cell growth arrest, mitochondrial damage, and apoptosis induction. Data obtained on primary hematopoietic malignant cells confirmed the FAO inhibition and cytotoxic activity of ST1326, particularly on acute myeloid leukemia cells. These data suggest that leukemia treatment may be carried out by targeting metabolic processes.
Oncogene. 2015 Oct 12.   http://dx.doi.org:/10.1038/onc.2015.394. [Epub ahead of print]
Tumour-suppression function of KLF12 through regulation of anoikis.
Suppression of detachment-induced cell death, known as anoikis, is an essential step for cancer metastasis to occur. We report here that expression of KLF12, a member of the Kruppel-like family of transcription factors, is downregulated in lung cancer cell lines that have been selected to grow in the absence of cell adhesion. Knockdown of KLF12 in parental cells results in decreased apoptosis following cell detachment from matrix. KLF12 regulates anoikis by promoting the cell cycle transition through S phase and therefore cell proliferation. Reduced expression levels of KLF12 results in increased ability of lung cancer cells to form tumours in vivo and is associated with poorer survival in lung cancer patients. We therefore identify KLF12 as a novel metastasis-suppressor gene whose loss of function is associated with anoikis resistance through control of the cell cycle.
Mol Cell. 2015 Oct 14. pii: S1097-2765(15)00764-9. doi: 10.1016/j.molcel.2015.09.025. [Epub ahead of print]
PEPCK Coordinates the Regulation of Central Carbon Metabolism to Promote Cancer Cell Growth.
Phosphoenolpyruvate carboxykinase (PEPCK) is well known for its role in gluconeogenesis. However, PEPCK is also a key regulator of TCA cycle flux. The TCA cycle integrates glucose, amino acid, and lipid metabolism depending on cellular needs. In addition, biosynthetic pathways crucial to tumor growth require the TCA cycle for the processing of glucose and glutamine derived carbons. We show here an unexpected role for PEPCK in promoting cancer cell proliferation in vitro and in vivo by increasing glucose and glutamine utilization toward anabolic metabolism. Unexpectedly, PEPCK also increased the synthesis of ribose from non-carbohydrate sources, such as glutamine, a phenomenon not previously described. Finally, we show that the effects of PEPCK on glucose metabolism and cell proliferation are in part mediated via activation of mTORC1. Taken together, these data demonstrate a role for PEPCK that links metabolic flux and anabolic pathways to cancer cell proliferation.
Mol Cancer Res. 2015 Oct;13(10):1408-20.   http://dx.doi.org:/10.1158/1541-7786.MCR-15-0048. Epub 2015 Jun 16.
Disruption of Proline Synthesis in Melanoma Inhibits Protein Production Mediated by the GCN2 Pathway.
Many processes are deregulated in melanoma cells and one of those is protein production. Although much is known about protein synthesis in cancer cells, effective ways of therapeutically targeting this process remain an understudied area of research. A process that is upregulated in melanoma compared with normal melanocytes is proline biosynthesis, which has been linked to both oncogene and tumor suppressor pathways, suggesting an important convergent point for therapeutic intervention. Therefore, an RNAi screen of a kinase library was undertaken, identifying aldehyde dehydrogenase 18 family, member A1 (ALDH18A1) as a critically important gene in regulating melanoma cell growth through proline biosynthesis. Inhibition of ALDH18A1, the gene encoding pyrroline-5-carboxylate synthase (P5CS), significantly decreased cultured melanoma cell viability and tumor growth. Knockdown of P5CS using siRNA had no effect on apoptosis, autophagy, or the cell cycle but cell-doubling time increased dramatically suggesting that there was a general slowdown in cellular metabolism. Mechanistically, targeting ALDH18A1 activated the serine/threonine protein kinase GCN2 (general control nonderepressible 2) to inhibit protein synthesis, which could be reversed with proline supplementation. Thus, targeting ALDH18A1 in melanoma can be used to disrupt proline biosynthesis to limit cell metabolism thereby increasing the cellular doubling time mediated through the GCN2 pathway.  This study demonstrates that melanoma cells are sensitive to disruption of proline synthesis and provides a proof-of-concept that the proline synthesis pathway can be therapeutically targeted in melanoma tumors for tumor inhibitory efficacy. Mol Cancer Res; 13(10); 1408-20. ©2015 AACR.
SDHB-Deficient Cancers: The Role of Mutations That Impair Iron Sulfur Cluster Delivery.
BACKGROUND:  Mutations in the Fe-S cluster-containing SDHB subunit of succinate dehydrogenase cause familial cancer syndromes. Recently the tripeptide motif L(I)YR was identified in the Fe-S recipient protein SDHB, to which the cochaperone HSC20 binds.
METHODS:   In order to characterize the metabolic basis of SDH-deficient cancers we performed stable isotope-resolved metabolomics in a novel SDHB-deficient renal cell carcinoma cell line and conducted bioinformatics and biochemical screening to analyze Fe-S cluster acquisition and assembly of SDH in the presence of other cancer-causing SDHB mutations.

RESULTS:

We found that the SDHB(R46Q) mutation in UOK269 cells disrupted binding of HSC20, causing rapid degradation of SDHB. In the absence of SDHB, respiration was undetectable in UOK269 cells, succinate was elevated to 351.4±63.2 nmol/mg cellular protein, and glutamine became the main source of TCA cycle metabolites through reductive carboxylation. Furthermore, HIF1α, but not HIF2α, increased markedly and the cells showed a strong DNA CpG island methylator phenotype (CIMP). Biochemical and bioinformatic screening revealed that 37% of disease-causing missense mutations in SDHB were located in either the L(I)YR Fe-S transfer motifs or in the 11 Fe-S cluster-ligating cysteines.

CONCLUSIONS:

These findings provide a conceptual framework for understanding how particular mutations disproportionately cause the loss of SDH activity, resulting in accumulation of succinate and metabolic remodeling in SDHB cancer syndromes.

 

SR4 Uncouples Mitochondrial Oxidative Phosphorylation, Modulates AMPK-mTOR Signaling, and Inhibits Proliferation of HepG2 Hepatocarcinoma Cells

  1. L. Figarola, J. Singhal, J. D. Tompkins, G. W. Rogers, C. Warden, D. Horne, A. D. Riggs, S. Awasthi and S. S. Singhal.

J Biol Chem. 2015 Nov 3, [epub ahead of print]

 

CD47 Receptor Globally Regulates Metabolic Pathways That Control Resistance to Ionizing Radiation

  1. W. Miller, D. R. Soto-Pantoja, A. L. Schwartz, J. M. Sipes, W. G. DeGraff, L. A. Ridnour, D. A. Wink and D. D. Roberts.

J Biol Chem. 2015 Oct 9, 290 (41): 24858-74.

 

Knockdown of PKM2 Suppresses Tumor Growth and Invasion in Lung Adenocarcinoma

  1. Sun, A. Zhu, L. Zhang, J. Zhang, Z. Zhong and F. Wang.

Int J Mol Sci. 2015 Oct 15, 16 (10): 24574-87.

 

EglN2 associates with the NRF1-PGC1alpha complex and controls mitochondrial function in breast cancer

  1. Zhang, C. Wang, X. Chen, M. Takada, C. Fan, X. Zheng, H. Wen, Y. Liu, C. Wang, R. G. Pestell, K. M. Aird, W. G. Kaelin, Jr., X. S. Liu and Q. Zhang.

EMBO J. 2015 Oct 22, [epub ahead of print]

 

Mitochondrial Genetics Regulate Breast Cancer Tumorigenicity and Metastatic Potential.

Current paradigms of carcinogenic risk suggest that genetic, hormonal, and environmental factors influence an individual’s predilection for developing metastatic breast cancer. Investigations of tumor latency and metastasis in mice have illustrated differences between inbred strains, but the possibility that mitochondrial genetic inheritance may contribute to such differences in vivo has not been directly tested. In this study, we tested this hypothesis in mitochondrial-nuclear exchange mice we generated, where cohorts shared identical nuclear backgrounds but different mtDNA genomes on the background of the PyMT transgenic mouse model of spontaneous mammary carcinoma. In this setting, we found that primary tumor latency and metastasis segregated with mtDNA, suggesting that mtDNA influences disease progression to a far greater extent than previously appreciated. Our findings prompt further investigation into metabolic differences controlled by mitochondrial process as a basis for understanding tumor development and metastasis in individual subjects. Importantly, differences in mitochondrial DNA are sufficient to fundamentally alter disease course in the PyMT mouse mammary tumor model, suggesting that functional metabolic differences direct early tumor growth and metastatic efficiency. Cancer Res; 75(20); 4429-36. ©2015 AACR.

 

Cancer Lett. 2015 Oct 29. pii: S0304-3835(15)00656-4.    http://dx.doi.org:/10.1016/j.canlet.2015.10.025. [Epub ahead of print]
Carboxyamidotriazole inhibits oxidative phosphorylation in cancer cells and exerts synergistic anti-cancer effect with glycolysis inhibition.

Targeting cancer cell metabolism is a promising strategy against cancer. Here, we confirmed that the anti-cancer drug carboxyamidotriazole (CAI) inhibited mitochondrial respiration in cancer cells for the first time and found a way to enhance its anti-cancer activity by further disturbing the energy metabolism. CAI promoted glucose uptake and lactate production when incubated with cancer cells. The oxidative phosphorylation (OXPHOS) in cancer cells was inhibited by CAI, and the decrease in the activity of the respiratory chain complex I could be one explanation. The anti-cancer effect of CAI was greatly potentiated when being combined with 2-deoxyglucose (2-DG). The cancer cells treated with the combination of CAI and 2-DG were arrested in G2/M phase. The apoptosis and necrosis rates were also increased. In a mouse xenograft model, this combination was well tolerated and retarded the tumor growth. The impairment of cancer cell survival was associated with significant cellular ATP decrease, suggesting that the combination of CAI and 2-DG could be one of the strategies to cause dual inhibition of energy pathways, which might be an effective therapeutic approach for a broad spectrum of tumors.

 

Cancer Immunol Res. 2015 Nov;3(11):1236-47.    http://dx.doi.org:/10.1158/2326-6066.CIR-15-0036. Epub 2015 May 29.
Inhibition of Fatty Acid Oxidation Modulates Immunosuppressive Functions of Myeloid-Derived Suppressor Cells and Enhances Cancer Therapies.

Myeloid-derived suppressor cells (MDSC) promote tumor growth by inhibiting T-cell immunity and promoting malignant cell proliferation and migration. The therapeutic potential of blocking MDSC in tumors has been limited by their heterogeneity, plasticity, and resistance to various chemotherapy agents. Recent studies have highlighted the role of energy metabolic pathways in the differentiation and function of immune cells; however, the metabolic characteristics regulating MDSC remain unclear. We aimed to determine the energy metabolic pathway(s) used by MDSC, establish its impact on their immunosuppressive function, and test whether its inhibition blocks MDSC and enhances antitumor therapies. Using several murine tumor models, we found that tumor-infiltrating MDSC (T-MDSC) increased fatty acid uptake and activated fatty acid oxidation (FAO). This was accompanied by an increased mitochondrial mass, upregulation of key FAO enzymes, and increased oxygen consumption rate. Pharmacologic inhibition of FAO blocked immune inhibitory pathways and functions in T-MDSC and decreased their production of inhibitory cytokines. FAO inhibition alone significantly delayed tumor growth in a T-cell-dependent manner and enhanced the antitumor effect of adoptive T-cell therapy. Furthermore, FAO inhibition combined with low-dose chemotherapy completely inhibited T-MDSC immunosuppressive effects and induced a significant antitumor effect. Interestingly, a similar increase in fatty acid uptake and expression of FAO-related enzymes was found in human MDSC in peripheral blood and tumors. These results support the possibility of testing FAO inhibition as a novel approach to block MDSC and enhance various cancer therapies. Cancer Immunol Res; 3(11); 1236-47. ©2015 AACR.

 

Ionizing radiation induces myofibroblast differentiation via lactate dehydrogenase

  1. L. Judge, K. M. Owens, S. J. Pollock, C. F. Woeller, T. H. Thatcher, J. P. Williams, R. P. Phipps, P. J. Sime and R. M. Kottmann.

Am J Physiol Lung Cell Mol Physiol. 2015 Oct 15, 309 (8): L879-87.

 

Vitamin C selectively kills KRAS and BRAF mutant colorectal cancer cells by targeting GAPDH

  1. Yun, E. Mullarky, C. Lu, K. N. Bosch, A. Kavalier, K. Rivera, J. Roper, Chio, II, E. G. Giannopoulou, C. Rago, A. Muley, J. M. Asara, J. Paik, O. Elemento, Z. Chen, D. J. Pappin, L. E. Dow, N. Papadopoulos, S. S. Gross and L. C. Cantley.

Science. 2015 Nov 5, [epub ahead of print]

 

Down-regulation of FBP1 by ZEB1-mediated repression confers to growth and invasion in lung cancer cells

  1. Zhang, J. Wang, H. Xing, Q. Li, Q. Zhao and J. Li.

Mol Cell Biochem. 2015 Nov 6, [epub ahead of print]

 

J Mol Cell Cardiol. 2015 Oct 23. pii: S0022-2828(15)30073-0.     http://dx.doi.org:/10.1016/j.yjmcc.2015.10.002. [Epub ahead of print]
GRK2 compromises cardiomyocyte mitochondrial function by diminishing fatty acid-mediated oxygen consumption and increasing superoxide levels.

The G protein-coupled receptor kinase-2 (GRK2) is upregulated in the injured heart and contributes to heart failure pathogenesis. GRK2 was recently shown to associate with mitochondria but its functional impact in myocytes due to this localization is unclear. This study was undertaken to determine the effect of elevated GRK2 on mitochondrial respiration in cardiomyocytes. Sub-fractionation of purified cardiac mitochondria revealed that basally GRK2 is found in multiple compartments. Overexpression of GRK2 in mouse cardiomyocytes resulted in an increased amount of mitochondrial-based superoxide. Inhibition of GRK2 increased oxygen consumption rates and ATP production. Moreover, fatty acid oxidation was found to be significantly impaired when GRK2 was elevated and was dependent on the catalytic activity and mitochondrial localization of this kinase. Our study shows that independent of cardiac injury, GRK2 is localized in the mitochondria and its kinase activity negatively impacts the function of this organelle by increasing superoxide levels and altering substrate utilization for energy production.

 

Br J Pharmacol. 2015 Oct 27. doi: 10.1111/bph.13377. [Epub ahead of print]
All-trans retinoic acid protects against doxorubicin-induced cardiotoxicity by activating the Erk2 signalling pathway.
BACKGROUND AND PURPOSE:

Doxorubicin (Dox) is a powerful antineoplastic agent for treating a wide range of cancers. However, doxorubicin cardiotoxicity of the heart has largely limited its clinical use. It is known that all-trans retinoic acid (ATRA) plays important roles in many cardiac biological processes, however, the protective effects of ATRA on doxorubicin cardiotoxicity remain unknown. Here, we studied the effect of ATRA on doxorubicin cardiotoxicity and underlying mechanisms.

EXPERIMENTAL APPROACHES:

Cellular viability assays, western blotting and mitochondrial respiration analyses were employed to evaluate the cellular response to ATRA in H9c2 cells and primary cardiomyocytes. Quantitative PCR (Polymerase Chain Reaction) and gene knockdown were performed to investigate the underlying molecular mechanisms of ATRA’s effects on doxorubicin cardiotoxicity.

KEY RESULTS:

ATRA significantly inhibited doxorubicin-induced apoptosis in H9c2 cells and primary cardiomyocytes. ATRA was more effective against doxorubicin cardiotoxicity than resveratrol and dexrazoxane. ATRA also suppressed reactive oxygen species (ROS) generation, and restored the expression level of mRNA and proteins in phase II detoxifying enzyme system: Nrf2 (nuclear factor-E2-related factor 2), MnSOD (manganese superoxide dismutase), HO-1 (heme oxygenase1) as well as mitochondrial function (mitochondrial membrane integrity, mitochondrial DNA copy numbers, mitochondrial respiration capacity, biogenesis and dynamics). Both Erk1/2 (extracellular signal-regulated kinase1/2) inhibitor (U0126) and Erk2 siRNA, but not Erk1 siRNA, abolished the protective effect of ATRA against doxorubicin-induced toxicity in H9c2 cells. Remarkably, ATRA did not compromise the anticancer efficacy of doxorubicin in gastric carcinoma cells.

CONCLUSION AND IMPLICATION:

ATRA protected cardiomyocytes against doxorubicin-induced toxicity by activating the Erk2 pathway without compromising the anticancer efficacy of doxorubicin. Therefore, ATRA may be a promising candidate as a cardioprotective agent against doxorubicin cardiotoxicity.

 

Proteomic and Biochemical Studies of Lysine Malonylation Suggest Its Malonic Aciduria-associated Regulatory Role in Mitochondrial Function and Fatty Acid Oxidation

  1. Colak, O. Pougovkina, L. Dai, M. Tan, H. Te Brinke, H. Huang, Z. Cheng, J. Park, X. Wan, X. Liu, W. W. Yue, R. J. Wanders, J. W. Locasale, D. B. Lombard, V. C. de Boer and Y. Zhao.

Mol Cell Proteomics. 2015 Nov 1, 14 (11): 3056-71.

 

Foxg1 localizes to mitochondria and coordinates cell differentiation and bioenergetics

  1. Pancrazi, G. Di Benedetto, L. Colombaioni, G. Della Sala, G. Testa, F. Olimpico, A. Reyes, M. Zeviani, T. Pozzan and M. Costa.

Proc Natl Acad Sci U S A. 2015 Oct 27, 112(45): 13910-5.

 

Evidence of Mitochondrial Dysfunction within the Complex Genetic Etiology of Schizophrenia

  1. E. Hjelm, B. Rollins, F. Mamdani, J. C. Lauterborn, G. Kirov, G. Lynch, C. M. Gall, A. Sequeira and M. P. Vawter.

Mol Neuropsychiatry. 2015 Nov 1, 1 (4): 201-219.

 

Metabolic Reprogramming Is Required for Myofibroblast Contractility and Differentiation

  1. Bernard, N. J. Logsdon, S. Ravi, N. Xie, B. P. Persons, S. Rangarajan, J. W. Zmijewski, K. Mitra, G. Liu, V. M. Darley-Usmar and V. J. Thannickal.

J Biol Chem. 2015 Oct 16, 290 (42): 25427-38.

 

J Biol Chem. 2015 Oct 23;290(43):25834-46.    http://dx.doi.org:/10.1074/jbc.M115.658815. Epub 2015 Sep 4.
Kinome Screen Identifies PFKFB3 and Glucose Metabolism as Important Regulators of the Insulin/Insulin-like Growth Factor (IGF)-1 Signaling Pathway.

The insulin/insulin-like growth factor (IGF)-1 signaling pathway (ISP) plays a fundamental role in long term health in a range of organisms. Protein kinases including Akt and ERK are intimately involved in the ISP. To identify other kinases that may participate in this pathway or intersect with it in a regulatory manner, we performed a whole kinome (779 kinases) siRNA screen for positive or negative regulators of the ISP, using GLUT4 translocation to the cell surface as an output for pathway activity. We identified PFKFB3, a positive regulator of glycolysis that is highly expressed in cancer cells and adipocytes, as a positive ISP regulator. Pharmacological inhibition of PFKFB3 suppressed insulin-stimulated glucose uptake, GLUT4 translocation, and Akt signaling in 3T3-L1 adipocytes. In contrast, overexpression of PFKFB3 in HEK293 cells potentiated insulin-dependent phosphorylation of Akt and Akt substrates. Furthermore, pharmacological modulation of glycolysis in 3T3-L1 adipocytes affected Akt phosphorylation. These data add to an emerging body of evidence that metabolism plays a central role in regulating numerous biological processes including the ISP. Our findings have important implications for diseases such as type 2 diabetes and cancer that are characterized by marked disruption of both metabolism and growth factor signaling.

 

FASEB J. 2015 Oct 19.    http://dx.doi.org:/pii: fj.15-276360. [Epub ahead of print]
Perm1 enhances mitochondrial biogenesis, oxidative capacity, and fatigue resistance in adult skeletal muscle.

Skeletal muscle mitochondrial content and oxidative capacity are important determinants of muscle function and whole-body health. Mitochondrial content and function are enhanced by endurance exercise and impaired in states or diseases where muscle function is compromised, such as myopathies, muscular dystrophies, neuromuscular diseases, and age-related muscle atrophy. Hence, elucidating the mechanisms that control muscle mitochondrial content and oxidative function can provide new insights into states and diseases that affect muscle health. In past studies, we identified Perm1 (PPARGC1- and ESRR-induced regulator, muscle 1) as a gene induced by endurance exercise in skeletal muscle, and regulating mitochondrial oxidative function in cultured myotubes. The capacity of Perm1 to regulate muscle mitochondrial content and function in vivo is not yet known. In this study, we use adeno-associated viral (AAV) vectors to increase Perm1 expression in skeletal muscles of 4-wk-old mice. Compared to control vector, AAV1-Perm1 leads to significant increases in mitochondrial content and oxidative capacity (by 40-80%). Moreover, AAV1-Perm1-transduced muscles show increased capillary density and resistance to fatigue (by 33 and 31%, respectively), without prominent changes in fiber-type composition. These findings suggest that Perm1 selectively regulates mitochondrial biogenesis and oxidative function, and implicate Perm1 in muscle adaptations that also occur in response to endurance exercise.-Cho, Y., Hazen, B. C., Gandra, P. G., Ward, S. R., Schenk, S., Russell, A. P., Kralli, A. Perm1 enhances mitochondrial biogenesis, oxidative capacity, and fatigue resistance in adult skeletal muscle.

 

A conserved MADS-box phosphorylation motif regulates differentiation and mitochondrial function in skeletal, cardiac, and smooth muscle cells.
Exposure to metabolic disease during fetal development alters cellular differentiation and perturbs metabolic homeostasis, but the underlying molecular regulators of this phenomenon in muscle cells are not completely understood. To address this, we undertook a computational approach to identify cooperating partners of the myocyte enhancer factor-2 (MEF2) family of transcription factors, known regulators of muscle differentiation and metabolic function. We demonstrate that MEF2 and the serum response factor (SRF) collaboratively regulate the expression of numerous muscle-specific genes, including microRNA-133a (miR-133a). Using tandem mass spectrometry techniques, we identify a conserved phosphorylation motif within the MEF2 and SRF Mcm1 Agamous Deficiens SRF (MADS)-box that regulates miR-133a expression and mitochondrial function in response to a lipotoxic signal. Furthermore, reconstitution of MEF2 function by expression of a neutralizing mutation in this identified phosphorylation motif restores miR-133a expression and mitochondrial membrane potential during lipotoxicity. Mechanistically, we demonstrate that miR-133a regulates mitochondrial function through translational inhibition of a mitophagy and cell death modulating protein, called Nix. Finally, we show that rodents exposed to gestational diabetes during fetal development display muscle diacylglycerol accumulation, concurrent with insulin resistance, reduced miR-133a, and elevated Nix expression, as young adult rats. Given the diverse roles of miR-133a and Nix in regulating mitochondrial function, and proliferation in certain cancers, dysregulation of this genetic pathway may have broad implications involving insulin resistance, cardiovascular disease, and cancer biology.

 

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Rheumatoid arthritis update

Larry H. Bernstein, MD, FCAP, Curator

LPBI

 

Innovation update: Advancing the standard of care in rheumatoid arthritis 

Old innovation makes way for new innovation

Twenty years ago, the standard of care for RA was some combination of basic NSAIDS, along with methotrexate. Caregivers focused on symptom relief, and it was widely understood that many patients would fail to achieve remission. As the disease developed, patients would eventually develop severely life-limiting disabilities as their disease progressed.

During this period, researchers presenting at conferences grew excited about data on a new class of drugs known as anti-tumor necrosis factor (TNF) antibodies. In an article published in Acta Orthopaedica Scandinavica in 1995, two physician-researchers wrote the following:

“Primary results have recently been published on the use of anti-TNF monoclonal antibodies. In a controlled trial these antibodies were able to significantly influence a number of disease-activity variables in RA. An important observation was that the clinical effect lasted from weeks to, in some cases, months.  Although the potential of these agents for clinical use is still uncertain, these observations suggest that interfering with certain targets of the immune-inflammatory process is possible, effective and so far without side effects.”

About four years after Drs. Van de Putte and Van Riel extolled the virtues of disease-modifying biologics in clinical trials, the first anti-TNF antibody, Remicade (infliximab) was approved in 1999. At that point, the standard of care for RA improved significantly, forever changing the treatment paradigm for patients with RA.

 

The expanding class of JAK inhibitors

At this year’s ACR meeting, researchers  focused on  anti-inflammatory antibodies and a relatively new class of oral drugs known as janus kinase (JAK) inhibitors.  Interest in JAK inhibitors has spiked since the approval of Pfizer’s oral medication Xeljanz (tofacitinib) —the first, and currently the only, JAK inhibitor approved for the treatment of moderate-to-severe RA.JAK inhibitors have garnered interest because of the role they can play in expanding a treatment area dominated by synthetic and biologic disease-modifying anti-rheumatic drugs (DMARDs). Could JAK inhibitors provide the breakthrough in RA that the anti-TNF antibodies provided almost 20 years ago?

Currently, Eli Lilly and Incyte are in late-stage development of baricitinib, a JAK1/JAK2 inhibitor for treatment of RA. Until last December, Johnson & Johnson (J&J) and Astellas were working jointly on another JAK inhibitor, known as ASPO15K, but J&J exercised its opt-out option and left the partnership. Astellas vowed to go it alone or look for a new partner, but there have not been many updates on ASPO15K within the last year.

 

Innovation means understanding and responding to unmet needs

Like many other therapeutic areas, RA treatments are often used in combination. For some patients, the combination of methotrexate and a powerful biologic, such as Remicade (infliximab), will help a patient achieve remission Yet others will either not respond to methotrexate and Remicade, or will have a negative reaction. Understanding how to help nonresponders achieve relief has become a key area of research in RA.

According to Terence Rooney, MD, Medical Director at Lilly Bio-Medicines, “A substantial proportion of patients treated with methotrexate – commonly used across the disease continuum for 25 years – do not achieve satisfactory disease control, signaling a need for more effective RA treatment options. In addition, studies have shown that some patients who initially respond to biologics lose response over time, and approximately 40 percent of patients with high disease activity never respond adequately to TNF antagonist biologics.”

 

Innovative clinical trial design

As Lilly and Incyte approach the end of the development process for baricitinib, they have been collecting results from clinical trials designed to both establish basic efficacy and safety in placebo-controlled and comparator trials, and to obtain data on targeted patient populations.

According to Rooney, “The baricitinib phase three program investigated the benefit of baricitinib across the spectrum of patients with rheumatoid arthritis, including newly diagnosed patients, patients who had failed to respond to conventional DMARDs, and patients who had failed multiple injectable biologic DMARD therapies.”

“In addition, the phase 3 program included two 52-week studies that incorporated either methotrexate or adalimumab as active comparators to provide useful information for therapeutic positioning of baricitinib. In these studies, baricitinib was statistically superior to methotrexate and to adalimumab in improving signs and symptoms, physical function, and important patient-reported outcomes including pain, fatigue and stiffness.”

Rooney also pointed out that there is additional data establishing baricitinib as a DMARD that significantly inhibits progressive radiographic joint damage.

 

Experience plus evidence equals more innovation

As has become the norm, companies at ACR often highlight new data confirming the efficacy and safety of already approved drugs in larger patient populations and in real-world settings..

Lilly currently has data on more than 40,000 patients worldwide, reflecting its global ambitions. Assuming that baricitinib is approved next year (the goal is to file at the end of the year), Lilly will continue to present data at ACR in the coming years highlighting the results of its long-term extension study, RA-BEYOND.

 

Pfizer’s up-to-date Xeljanz data presentation at ACR

Although Xeljanz has been on the market for three years in more than 40 countries, Pfizer continues to focus on collecting new data and using it to expand use of Xeljanz. In fact, Pfizer had 20 abstracts focused solely on Xeljanz at ACR 2015.

According to Rory O’Connor, MD, Senior Vice President and Head of Global Medical Affairs, Global Innovative Pharmaceuticals Business, Pfizer, “Ongoing clinical trials and long-term extension studies provide important information about the safety and efficacy of Xeljanz in RA. We are focused on continuing to build on our knowledge of the clinical application of Xeljanz in real-world settings.”

Pfizer was also able to highlight new data that supports their recent NDA for Xeljanz XR, a once-daily formulation of Xeljanz, which is currently approved as a twice-daily dosing formulation.

 

JAK inhibition beyond RA

One of the most exciting things about the progress with JAK inhibitors is the possibility to innovate treatments beyond RA. Lilly has been exploring the role of JAK-dependent cytokines in the pathogenesis of numerous inflammatory and autoimmune diseases. The company also plans to meet with regulatory authorities to develop a pediatric program for juvenile RA and idiopathic arthritis.

Meanwhile, Pfizer has developed a broad portfolio of various JAK inhibitors and therapies with new modes of action. Already, Pfizer researchers have completed two phase three studies in ulcerative colitis and the top-line results have been positive.

Medical meetings are exciting, because they provide a forum for discussing breakthroughs and portending a future in which the standard of care improves. For companies like Lilly, Incyte, and Pfizer, continual development of more novel approaches to serious diseasesis like a call-response echo chamber in which innovation drives more innovation, resulting in better long-term outcomes for patients.

 

 

The JAK/STAT signaling pathway
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In addition to the principal components of the pathway, other effector proteins have been identified that contribute to at least a subset of JAK/STAT signaling events. STAMs (signal-transducing adapter molecules) are adapter molecules with conserved VHS and SH3 domains (Lohi and Lehto, 2001). STAM1 and STAM2A can be phosphorylated by JAK1-JAK3 in a manner that is dependent on a third domain present in some STAMs, the ITAM (inducible tyrosine-based activation motif). Through a poorly understood mechanism, the STAMs facilitate the transcriptional activation of specific target genes, including MYC. A second adapter that facilitates JAK/STAT pathway activation is StIP (stat-interacting protein), a WD40 protein. StIPs can associate with both JAKs and unphosphorylated STATs, perhaps serving as a scaffold to facilitate the phosphorylation of STATs by JAKs. A third class of adapter with function in JAK/STAT signaling is the SH2B/Lnk/APS family. These proteins contain both pleckstrin homology and SH2 domains and are also substrates for JAK phosphorylation. Both SH2-Bβ and APS associate with JAKs, but the former facilitates JAK/STAT signaling while the latter inhibits it. The degree to which each of these adapter families contributes to JAK/STAT signaling is not yet well understood, but it is clear that various proteins outside the basic pathway machinery influence JAK/STAT signaling.

In addition to JAK/STAT pathway effectors, there are three major classes of negative regulator: SOCS (suppressors of cytokine signaling), PIAS (protein inhibitors of activated stats) and PTPs (protein tyrosine phosphatases) (reviewed by Greenhalgh and Hilton, 2001). Perhaps the simplest are the tyrosine phosphatases, which reverse the activity of the JAKs. The best characterized of these is SHP-1, the product of the mouse motheaten gene. SHP-1 contains two SH2 domains and can bind to either phosphorylated JAKs or phosphorylated receptors to facilitate dephosphorylation of these activated signaling molecules. Other tyrosine phosphatases, such as CD45, appear to have a role in regulating JAK/STAT signaling through a subset of receptors.

SOCS proteins are a family of at least eight members containing an SH2 domain and a SOCS box at the C-terminus (reviewed by Alexander, 2002). In addition, a small kinase inhibitory region located N-terminal to the SH2 domain has been identified for SOCS1 and SOCS3. The SOCS complete a simple negative feedback loop in the JAK/STAT circuitry: activated STATs stimulate transcription of the SOCS genes and the resulting SOCS proteins bind phosphorylated JAKs and their receptors to turn off the pathway. The SOCS can affect their negative regulation by three means. First, by binding phosphotyrosines on the receptors, SOCS physically block the recruitment of signal transducers, such as STATs, to the receptor. Second, SOCS proteins can bind directly to JAKs or to the receptors to specifically inhibit JAK kinase activity. Third, SOCS interact with the elongin BC complex and cullin 2, facilitating the ubiquitination of JAKs and, presumably, the receptors. Ubiquitination of these targets decreases their stability by targeting them for proteasomal degradation.

The third class of negative regulator is the PIAS proteins: PIAS1, PIAS3, PIASx and PIASy. These proteins have a Zn-binding RING-finger domain in the central portion, a well-conserved SAP (SAF-A/Acinus/PIAS) domain at the N-terminus, and a less-well-conserved carboxyl domain. The latter domains are involved in target protein binding. The PIAS proteins bind to activated STAT dimers and prevent them from binding DNA. The mechanism by which PIAS proteins act remains unclear. However, PIAS proteins have recently been demonstrated to associate with the E2 conjugase Ubc9 and to have E3 conjugase activity for sumoylation that is mediated by the RING finger domain (reviewed by Jackson, 2001). Although there is evidence that STATs can be modified by sumoylation (Rogers et al., 2003), the function of that modification in negative regulation is not yet known.

Although the mechanism of JAK/STAT signaling is relatively simple in theory, the biological consequences of pathway activation are complicated by interactions with other signaling pathways (reviewed by Heinrich et al., 2003; Rane and Reddy, 2000; Shuai, 2000). An understanding of this cross-talk is only beginning to emerge, but the best characterized interactions of the JAK/STAT pathway are with the receptor tyrosine kinase (RTK)/Ras/MAPK (mitogen-activated protein kinase) pathway. The relationship between these cascades is complex and their paths cross at multiple levels, each enhancing activation of the other. First, activated JAKs can phosphorylate tyrosines on their associated receptors that can serve as docking sites for SH2-containing adapter proteins from other signaling pathways. These include SHP-2 and Shc, which recruit the GRB2 adapter and stimulate the Ras cascade. The same mechanism stimulates other cascades, such as the recruitment and JAK phosphorylation of insulin receptor substrate (IRS) and p85, which results in the activation of the phosphoinositide 3-kinase (PI3K) pathway [for more on PI3K signaling, see Foster et al. (Foster et al., 2003)]. JAK/STAT signaling also indirectly promotes Ras signaling through the transcriptional activation of SOCS3. SOCS3 binds RasGAP, a negative regulator of Ras signaling, and reduces its activity, thereby promoting activation of the Ras pathway. Reciprocally, RTK pathway activity promotes JAK/STAT signaling by at least two mechanisms. First, the activation of some RTKs, including EGFR and PDGFR, results in the JAK-independent tyrosine phosphorylation of STATs, probably by the Src kinase. Second, RTK/Ras pathway stimulation causes the downstream activation of MAPK. MAPK specifically phosphorylates a serine near the C-terminus of most STATs. While not absolutely necessary for STAT activity, this serine phosphorylation dramatically enhances transcriptional activation by STAT. In addition to RTK and PI3K interactions with JAK/STAT signaling, multiple levels of cross-talk with the TGF-β signaling pathway have been recently reported [for a review of TGF-β, see (Moustakas, 2002)]. Furthermore, the functions of activated STATs can be altered through association with other transcription factors and cofactors that are regulated by other signaling pathways. Thus the integration of input from many signaling pathways must be considered if we are to understand the biological consequences of cytokine stimulation.

References

…..

 

https://youtu.be/9JHBHSHaBeI

Published on 27 Feb 2014

The JAK/STAT secondary messenger signaliing pathway..
Presented by: Joseph Farahany, M.D

 

Jak/Stat Signaling Pathway

 

Jaks and Stats are critical components of many cytokine receptor systems; regulating growth, survival, differentiation, and pathogen resistance. An example of these pathways is shown for the IL-6 (or gp130) family of receptors, which coregulate B cell differentiation, plasmacytogenesis, and the acute phase reaction. Cytokine binding induces receptor dimerization, activating the associated Jaks, which phosphorylate themselves and the receptor. The phosphorylated sites on the receptor and Jaks serve as docking sites for the SH2-containing Stats, such as Stat3, and for SH2-containing proteins and adaptors that link the receptor to MAP kinase, PI3K/Akt, and other cellular pathways.

Phosphorylated Stats dimerize and translocate into the nucleus to regulate target gene transcription. Members of the suppressor of cytokine signaling (SOCS) family dampen receptor signaling via homologous or heterologous feedback regulation. Jaks or Stats can also participate in signaling through other receptor classes, as outlined in the Jak/Stat Utilization Table. Researchers have found Stat3 and Stat5 to be constitutively activated by tyrosine kinases other than Jaks in several solid tumors

The Jak/Stat pathway mediates the effects of cytokines, like erythropoietin, thrombopoietin, and G-CSF, which are protein drugs for the treatment of anemia, thrombocytopenia, and neutropenia, respectively. The pathway also mediates signaling by interferons, which are used as antiviral and antiproliferative agents. Researchers have found that dysregulated cytokine signaling contributes to cancer. Aberrant IL-6 signaling contributes to the pathogenesis of autoimmune diseases, inflammation, and cancers such as prostate cancer and multiple myeloma. Jak inhibitors currently are being tested in models of multiple myeloma. Stat3 can act as an oncogene and is constitutively active in many tumors. Crosstalk between cytokine signaling and EGFR family members is seen in some cancer cells. Research has shown that in glioblastoma cells overexpressing EGFR, resistance to EGFR kinase inhibitors is induced by Jak2 binding to EGFR via the FERM domain of the former [Sci. Signal. (2013) 6, ra55].

Activating Jak mutations are major molecular events in human hematological malignancies. Researchers have found a unique somatic mutation in the Jak2 pseudokinase domain (V617F) that commonly occurs in polycythemia vera, essential thrombocythemia, and idiopathic myelofibrosis. This mutation results in the pathologic activation Jak2, associated with receptors for erythropoietin, thrombopoietin, and G-CSF, which control erythroid, megakaryocytic, and granulocytic proliferation and differentiation. Researchers have also shown that somatic acquired gain-of-function mutations of Jak1 are found in adult T cell acute lymphoblastic leukemia. Somatic activating mutations in Jak1, Jak2, and Jak3 have also been identified in pediatric acute lymphoblastic leukemia (ALL). Furthermore, Jak2 mutations have been detected around pseudokinase domain R683 (R683G or DIREED) in Down syndrome childhood B-ALL and pediatric B-ALL.

Selected Reviews:

– See more at: http://www.cellsignal.com/contents/science-pathway-research-immunology-and-inflammation/jak-stat-signaling-pathway/pathways-il6#sthash.8SVwSWXw.dpuf

 

The JAK-STAT Signaling Pathway: Input and Output Integration1

  1. Peter J. Murray

The Journal of Immunology Mar 1, 2007;  178(5): 2623-2629    http://dx.doi.org:/10.4049/​jimmunol.178.5.2623

Universal and essential to cytokine receptor signaling, the JAK-STAT pathway is one of the best understood signal transduction cascades. Almost 40 cytokine receptors signal through combinations of four JAK and seven STAT family members, suggesting commonality across the JAK-STAT signaling system. Despite intense study, there remain substantial gaps in understanding how the cascades are activated and regulated. Using the examples of the IL-6 and IL-10 receptors, I will discuss how diverse outcomes in gene expression result from regulatory events that effect the JAK1-STAT3 pathway, common to both receptors. I also consider receptor preferences by different STATs and interpretive problems in the use of STAT-deficient cells and mice. Finally, I consider how the suppressor of cytokine signaling (SOCS) proteins regulate the quality and quantity of STAT signals from cytokine receptors. New data suggests that SOCS proteins introduce additional diversity into the JAK-STAT pathway by adjusting the output of activated STATs that alters downstream gene activation.

 

 

The mammalian JAK and STAT family members have been extensively, and seemingly exhaustively, analyzed in the mouse and human systems. All four JAK and seven STAT family members have been deleted in the mouse, in addition to the creation of conditional alleles for genes whose loss of function leads to embryonic or perinatal lethality (Stat3, combined deficiency of Stat5a and Stat5b, and Jak2). In humans, detailed genetic studies have been performed in people bearing mutant Jak or Stat genes. Specific Abs to phospho-forms of each protein are used to study how the JAK-STAT cascade is activated by cytokine receptors. Crystallographic studies have illuminated structural information for multiple STAT family members in different forms. Pharmacological inhibitors have been developed for clinical use where JAK-STAT signaling is implicated in disease pathology and progression. Finally, in most cases, a specific JAK-STAT combination has been paired with each cytokine receptor, and this information translated into cell-type specific patterns of cytokine responsiveness and gene expression.

Major questions remain concerning how the JAK-STAT cascade functions to control specific gene expression patterns, and how the cascades are regulated. I will describe three elements of JAK-STAT signaling that require experimental investigation. First, I will address an unexpected experimental complication that arises from the analysis of mice and cells that lack one or more STAT family member. Second, I will use JAK1-STAT3 signaling from the IL-10R and IL-6R systems to illustrate that we lack detailed understanding of how specificity in gene expression is generated by receptors that use identical JAK-STAT members. Third, we have yet to explain how STAT activation is negatively regulated. Although the suppressor of cytokine signaling (SOCS)3 proteins are the best understood negative regulators of the JAK-STAT pathway, the biochemical mechanism of SOCS-mediated inhibition is unexplained. Moreover, additional inhibitory pathways have also been proposed to block the production of activated STATs. Collectively, I will argue that our understanding of the pathway from cytokine receptor to gene expression profile is in its infancy, but remains one of the best opportunities to dissect signal transduction.

Overview of the proximal JAK-STAT activation mechanism

The current model of JAK-STAT signaling holds that cytokine receptor engagement activates the associated JAK combination, which in turn phosphorylates the receptor cytoplasmic domain to allow recruitment of a STAT, which in turn is phosphorylated, dimerizes and moves to the nucleus to bind specific sequences in the genome and activate gene expression. Cytoplasmic domains of cytokine receptors associate with JAKs via JAK binding sites located close to the membrane (1). The postulated role of JAKs in trafficking or chaperoning the receptors to the cell surface is debated (2, 3, 4, 5, 6). Regardless of the when and where cytokine receptors and JAKs associate, their close apposition at the membrane is required to stimulate the kinase activity of the JAK following cytokine binding. At this stage in the activation of the pathway, we understand next to nothing about the structural basis of the JAK-receptor interaction, how receptor intracellular domains reorient upon cytokine binding and physically contact the JAK to receive the phosphorylation modification.

JAK-mediated phosphorylation of the receptor creates binding sites for the Src homology 2 (SH2) domains of the STATs. STAT recruitment is followed by tyrosine, and in some cases, serine phosphorylation on key residues (by the JAKs and other closely associated kinases) that leads to transit into the nucleus. This brief summary of the activation of the JAK-STAT pathway omits numerous unresolved details: the STAT monomer to dimer transition has been questioned, as has the role of phosphorylation in dimerization and nuclear transit (7). Furthermore, it is unclear how many configurations of STAT homo- and heterocomplexes are present in cells before, during, and after cytokine stimulation (8, 9,10). We do not understand the detailed structural basis for the preference of one SH2 domain for a given receptor, and we have little knowledge of how other non-JAK kinases are recruited to the receptors and phosphorylate the STATs.

Many receptors signal through a small number of JAKs

Cytokine receptors signal through two types of pathways: the JAK-STAT pathway and other pathways that usually involve the activation of the MAP kinase cascade. Although the latter will not be discussed here, it is worth noting that elegant genetic studies have demonstrated the importance of these pathways in various pathological systems (11, 12,13, 14). There are now ∼36 cytokine receptor combinations that respond to ∼38 cytokines (counting the type I IFNs as one because they all signal through the IFN-αβR). Different cells and tissues express distinct receptor combinations that respond to cytokine combinations unique to the microenvironment or systemic response of the organism. Hence, at any given time, a single cell may integrate signals from multiple cytokine receptors. Genetic studies have established that the cytokine receptor system is restrictive in that different classes of receptors preferentially use one JAK or JAK combination (7): receptors required for hemopoietic cell development and proliferation use JAK2, common γ-chain receptors use JAK1 and JAK3 whereas other receptors use only JAK1 (Fig. 1). Unexplained is the selective use of these combinations: why the IFN-γR rigidly uses the JAK1, JAK2 combination is unknown as is the restricted use of TYK2. Compared with JAK1–3, TYK2 is unusual in that loss of function mutations in the mouse have shown obligate, but not absolute, requirements in IFN-αβR and IL-12R signaling (15, 16). In contrast, human TYK2 seems to be essential for signaling through a broader range of cytokine receptors (17).

 

FIGURE 1.

FIGURE 1.

The majority of cytokine receptors use three JAK combinations. Shown are well-studied cases where JAK usage by each cytokine receptor has been established by genetic and biochemical studies. Exceptions shown are the G-CSFR (∗) where it is currently unclear whether both JAK1 and JAK2 are required together. Additionally, the IL-12R (†) and IL-23R (†) require TYK2 but the requirement for JAK2 has not been definitively determined. Receptors that use JAK2 and JAK3, JAK3 alone, TYK2 alone, or JAK3 and TYK2 have not been described.

The preferential association of JAKs to certain receptor classes raises several issues. First, how did the JAK-receptor combinations evolve? Because the number of receptors is relatively large, why has the number of JAKs remained small? Why have the combinations of JAK pairs also remained small given that there are 10 possible combinations that can be used (Fig. 1)? Second, how flexible is the cytokine receptor-JAK pair? That is, can receptors be engineered for interchangeable JAK use, or is a given JAK combination fixed for a specific receptor class? For example, can JAK1, JAK3, or TYK2 activate erythropoietin receptor (EpoR) signaling (if so engineered) or is JAK2 obligatory for signaling? These questions allude to a fundamental issue that concerns the function of the JAK in cytokine receptor activation: if the only function of the JAKs is to phosphorylate tyrosine resides on the cytoplasmic domain of the receptors, then it should be possible to trade JAK-receptor pairs. If these receptors retain identical downstream gene expression profiles, then the signal generated by the JAK is generic and functions primarily to activate the receptor (6). Conversely, it is also possible that each receptor-JAK combination retains crucial specificity functions and swapping, for example, JAK1 for JAK2 on the EpoR will modify or destroy a specific function in erythrogenesis. These questions can be addressed experimentally by replacing one preferred JAK binding site for another in genes encoding different receptors. The EpoR is a good test example because the activity of the receptor and its signaling pathway is essential for life and erythropoiesis is readily assayed.

Core versus cell-type specific STAT signaling

Microarray experiments designed to monitor changes in gene expression induced by JAK-STAT signaling have revealed that both cell-type specific transcription and core, or stereotypic, mRNA profiles are induced by activated cytokine receptors in different cell types (Fig. 2). For example, IFN-γ, via STAT1, induces the expression of a similar cohort of genes regardless of the cell type tested (18). These genes are often termed the “IFN signature” and overlap with the gene expression pattern induced by IFN-αβ signaling that also involves STAT1, in cooperation with STAT2 and IRF9. The IFN signature is readily observed in microarray experiments and is indicative of STAT1 activity. The STAT6 pathway activated by IL-4 or IL-13 provides an example of a cell-type specific response. IL-4-regulated genes in T cells have a distinct signature compared with IL-4/IL-13 signaling in macrophages or other non-lymphocytes (19, 20, 21, 22). In the latter, genes such as Arg1(encoding arginase 1) are often induced >100-fold but are silent in T cells (23, 24, 25, 26,27). Collectively these data argue that STATs activate defined gene sets, depending on their genomic accessibility, and possibly on cofactors that further refine gene expression profiles. STAT3 signaling illustrates a more complex system and will be discussed below to illustrate the distinctions between IL-6 and IL-10 signaling.

 

FIGURE 2.

FIGURE 2.

Core signaling by STATs. Representative examples of gene expression induced by STAT signaling in different tissues. The examples were extracted and edited from numerous microarray and empirical studies.

Interpreting experiments using STAT loss-of-function systems

Experiments with the different STAT knockout mice, and cells derived from these animals, have been critical for understanding specific requirements of individual STATs in gene expression following cytokine receptor signaling. The interpretation of these experiments is generally straightforward. For example, STAT5a and STAT5b are essential for the expression of genes that promote hemopoietic survival (28, 29, 30) whereas STAT1 is required for the expression of IFN-regulated genes that are involved in the protection against pathogens (18). However, by EMSA and immunoblotting experiments, most cytokines have been shown to activate multiple STATs, prompting experiments to determine transcriptional responses that can be activated in the absence of a given STAT. An initial example of this type of approach was performed by Schreiber and colleagues who interrogated gene expression profiles induced by IFN-γ signaling in the absence of STAT1 (31, 32). In these experiments, IFN-γ was used to stimulate STAT1-deficient bone marrow-derived macrophages and fibroblasts. Numerous genes were induced by IFN-γ in the absence of STAT1, leading to the conclusion that the IFN-γR activates a STAT1-independent gene expression program. However, inspection of the genes induced by IFN-γ signaling in STAT1-deficient cells shows many to be STAT3-regulated genes such asSocs3, Gadd45, and Cebpb. STAT3 phosphorylation is normally induced by IFN-γ in wild-type cells but in the absence of STAT1, STAT3 signaling is dominant. What is the mechanism of this effect? We now know from experiments using STAT-deficient cells that receptor occupancy, or lack of occupancy by the dominant STAT that binds the receptor, causes a switch from one activated STAT to another (33). A converse example is the conversion of IL-6R signaling to a dominant STAT1 activation in STAT3-deficient cells (34). This switch causes the downstream induction of the IFN gene expression pathway just as IFN-γ would cause in wild-type cells.

A related example is observed when IL-6 signaling is tested in the absence of SOCS3. SOCS3 is induced by STAT signaling from different cytokine receptors and functions as a feedback inhibitor of the IL-6R (and the G-CSFR, LIFR, and leptinR) by binding to phosphorylated Y757 on the gp130 cytoplasmic domain (see below). However in the absence of SOCS3, STAT3 phosphorylation is greatly increased (35, 36, 37). At the same time however, STAT1 phosphorylation is also induced, leading to a dominant IFN-like gene expression signature (35, 36). Thus SOCS3 regulates both the quantity and type of STAT signal generated from the IL-6R. Although the mechanism of the SOCS3 effect is unclear, the promiscuity of different receptors for different STATs argues that loss-of-function experiments must be carefully examined for the activation of other STAT molecules that fill the “hole” created by the loss of one STAT. These data also suggest that different cytokine receptors have evolved selectivity for different classes of STATs. Although STAT1 and STAT3 can apparently interchangeably bind the IL-6R or IFN-γR when either molecule is missing, signaling in wild-type cells shows a strong preference for one STAT over the other. Likewise, other receptors may have evolved to bind only one STAT, and in the absence of the key STAT, the other STATs cannot bind and/or be activated by the receptor.

The above examples primarily describe experiments using STAT1–STAT3-activating receptors but these are not isolated cases. In T cells stimulated by IL-12, STAT4 is activated and drives IFN-γ production. This pathway is a central regulatory event in the development of the Th1 type T cell responses. IFN-αβ, via the IFN-αβR, also activates STAT4 (in addition to STAT1 and STAT2 that forms a complex with IRF-9 to mediate anti-viral gene expression) but cannot activate strong IFN-γ production and therefore cannot drive Th1 development (38). However, in the absence of STAT1, IFN-αβ causes a large increase in IFN-γ production, especially in vivo during viral infection (39, 40). These data were originally interpreted to mean that STAT1 normally suppressed IFN-γ production. However, the data can just as easily be resolved when we consider that STAT4 activation from the IFN-αβR is increased in the absence of STAT1. Recent data confirm this interpretation but also show that STAT4 activation by the IFN-αβR, although increased, cannot sustain IFN-γ production from T cells when compared with IL-12 (38). This is probably because of the stronger differential activity of SOCS1 on the IFN-αβR versus the IL-12R (discussed below). I would predict that an IFN-αβR that is refractory to SOCS1 (or active in a Socs1−/− background) would behave identically to the IL-12R in the absence of STAT1.

Although loss of gene expression may be observed in a given STAT knockout, a corresponding increase in the ectopic activation of another STAT pathway may confound the interpretation of results in both in vitro and in vivo systems. Because specific Abs are available for each tyrosine-phosphorylated STAT molecule, a simple solution is to first measure which other STATs are activated by a given receptor in the absence of the STAT of interest. Experiments using STAT knockout systems should also be supported by additional data that uses complimentary mutations in the receptor that ablate STAT recruitment, or complete loss of the receptor. Finally, it is worth noting that the loss of a STAT pathway from a receptor signaling system can cause additional loss of key negative regulatory systems including feedback loops such as SOCS induction as presently debated for G-CSFR signaling and receptor systems discussed below (41, 42, 43, 44, 45).

  1. Negative regulation of the JAK-STAT signal
  2. Is there functional equivalence in signaling from receptors using the same JAK-STAT combination in the same cell?
  3. Future directions

 

FIGURE 3.

FIGURE 3.

Proposed differential STAT activation by IL-10 or IL-6. Shown are three classes of genes activated by STAT3 where Socs3 is a representative “common” gene induced by both receptors. In the absence of SOCS3, the IL-6R can activate the anti-inflammatory genes in the same way as the IL-10R. The mechanism of this effect remains to be established.

 

JAK/STAT Activation Inhibitors

The JAK/STAT pathway plays an important role in cytokine receptor-mediated signal transduction via activation of downstream signal transducers and activators of transcription (STAT), phosphatidylinositol 3-kinase (PI3K), and mitogen-activated protein kinase (MAPK) pathways.
These inhibitors are useful tools for exploring the contribution of JAK/STAT-mediated signaling.

Pathways of inhibition of JAK/STAT activation

JAK/STAT Activation Inhibitors

AG490 JAK2 inhibitor 10 mg
AZD1480 NEW! JAK1 & JAK2 inhibitor 5 mg
CP-690550 JAK3 Inhibitor 5 mg
CYT387 NEW! JAK1/JAK2 & TBK1/IKK-ε inhibitor 10 mg
Ruxolitinib JAK1 & JAK2 Inhibitor 5 mg

 

Methotrexate Is a JAK/STAT Pathway Inhibitor

Sally Thomas, Katherine H. Fisher, John A. Snowden, Sarah J. Danson, Stephen Brown, Martin P. Zeidler

PLOS   Published: July 1, 2015
DOI: http://dx.doi.org:/10.1371/journal.pone.0130078
Background 

The JAK/STAT pathway transduces signals from multiple cytokines and controls haematopoiesis, immunity and inflammation. In addition, pathological activation is seen in multiple malignancies including the myeloproliferative neoplasms (MPNs). Given this, drug development efforts have targeted the pathway with JAK inhibitors such as ruxolitinib. Although effective, high costs and side effects have limited its adoption. Thus, a need for effective low cost treatments remains.

Methods & Findings        

We used the low-complexity Drosophila melanogaster pathway to screen for small molecules that modulate JAK/STAT signalling. This screen identified methotrexate and the closely related aminopterin as potent suppressors of STAT activation. We show that methotrexate suppresses human JAK/STAT signalling without affecting other phosphorylation-dependent pathways. Furthermore, methotrexate significantly reduces STAT5 phosphorylation in cells expressing JAK2 V617F, a mutation associated with most human MPNs. Methotrexate acts independently of dihydrofolate reductase (DHFR) and is comparable to the JAK1/2 inhibitor ruxolitinib. However, cells treated with methotrexate still retain their ability to respond to physiological levels of the ligand erythropoietin.

Conclusions

Aminopterin and methotrexate represent the first chemotherapy agents developed and act as competitive inhibitors of DHFR. Methotrexate is also widely used at low doses to treat inflammatory and immune-mediated conditions including rheumatoid arthritis. In this low-dose regime, folate supplements are given to mitigate side effects by bypassing the biochemical requirement for DHFR. Although independent of DHFR, the mechanism-of-action underlying the low-dose effects of methotrexate is unknown. Given that multiple pro-inflammatory cytokines signal through the pathway, we suggest that suppression of the JAK/STAT pathway is likely to be the principal anti-inflammatory and immunosuppressive mechanism-of-action of low-dose methotrexate. In addition, we suggest that patients with JAK/STAT-associated haematological malignancies may benefit from low-dose methotrexate treatments. While the JAK1/2 inhibitor ruxolitinib is effective, a £43,200 annual cost precludes widespread adoption. With an annual methotrexate cost of around £32, our findings represent an important development with significant future potential.

Citation: Thomas S, Fisher KH, Snowden JA, Danson SJ, Brown S, Zeidler MP (2015) Methotrexate Is a JAK/STAT Pathway Inhibitor. PLoS ONE 10(7): e0130078.   http://dx.doi.org:/10.1371/journal.pone.0130078

 

 

 

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Clinical Laboratory Challenges

Larry H. Bernstein, MD, FCAP, Curator

LPBI

 

CLINICAL LABORATORY NEWS   

The Lab and CJD: Safe Handling of Infectious Prion Proteins

Body fluids from individuals with possible Creutzfeldt-Jakob disease (CJD) present distinctive safety challenges for clinical laboratories. Sporadic, iatrogenic, and familial CJD (known collectively as classic CJD), along with variant CJD, kuru, Gerstmann-Sträussler-Scheinker, and fatal familial insomnia, are prion diseases, also known as transmissible spongiform encephalopathies. Prion diseases affect the central nervous system, and from the onset of symptoms follow a typically rapid progressive neurological decline. While prion diseases are rare, it is not uncommon for the most prevalent form—sporadic CJD—to be included in the differential diagnosis of individuals presenting with rapid cognitive decline. Thus, laboratories may deal with a significant number of possible CJD cases, and should have protocols in place to process specimens, even if a confirmatory diagnosis of CJD is made in only a fraction of these cases.

The Lab’s Role in Diagnosis

Laboratory protocols for handling specimens from individuals with possible, probable, and definitive cases of CJD are important to ensure timely and appropriate patient management. When the differential includes CJD, an attempt should be made to rule-in or out other causes of rapid neurological decline. Laboratories should be prepared to process blood and cerebrospinal fluid (CSF) specimens in such cases for routine analyses.

Definitive diagnosis requires identification of prion aggregates in brain tissue, which can be achieved by immunohistochemistry, a Western blot for proteinase K-resistant prions, and/or by the presence of prion fibrils. Thus, confirmatory diagnosis is typically achieved at autopsy. A probable diagnosis of CJD is supported by elevated concentration of 14-3-3 protein in CSF (a non-specific marker of neurodegeneration), EEG, and MRI findings. Thus, the laboratory may be required to process and send CSF samples to a prion surveillance center for 14-3-3 testing, as well as blood samples for sequencing of the PRNP gene (in inherited cases).

Processing Biofluids

Laboratories should follow standard protective measures when working with biofluids potentially containing abnormally folded prions, such as donning standard personal protective equipment (PPE); avoiding or minimizing the use of sharps; using single-use disposable items; and processing specimens to minimize formation of aerosols and droplets. An additional safety consideration is the use of single-use disposal PPE; otherwise, re-usable items must be either cleaned using prion-specific decontamination methods, or destroyed.

Blood. In experimental models, infectivity has been detected in the blood; however, there have been no cases of secondary transmission of classical CJD via blood product transfusions in humans. As such, blood has been classified, on epidemiological evidence by the World Health Organization (WHO), as containing “no detectible infectivity,” which means it can be processed by routine methods. Similarly, except for CSF, all other body fluids contain no infectivity and can be processed following standard procedures.

In contrast to classic CJD, there have been four cases of suspected secondary transmission of variant CJD via transfused blood products in the United Kingdom. Variant CJD, the prion disease associated with mad cow disease, is unique in its distribution of prion aggregates outside of the central nervous system, including the lymph nodes, spleen, and tonsils. For regions where variant CJD is a concern, laboratories should consult their regulatory agencies for further guidance.

CSF. Relative to highly infectious tissues of the brain, spinal cord, and eye, infectivity has been identified less often in CSF and is considered to have “low infectivity,” along with kidney, liver, and lung tissue. Since CSF can contain infectious material, WHO has recommended that analyses not be performed on automated equipment due to challenges associated with decontamination. Laboratories should perform a risk assessment of their CSF processes, and, if deemed necessary, consider using manual methods as an alternative to automated systems.

Decontamination

The infectious agent in prion disease is unlike any other infectious pathogen encountered in the laboratory; it is formed of misfolded and aggregated prion proteins. This aggregated proteinacious material forms the infectious unit, which is incredibly resilient to degradation. Moreover, in vitro studies have demonstrated that disrupting large aggregates into smaller aggregates increases cytotoxicity. Thus, if the aim is to abolish infectivity, all aggregates must be destroyed. Disinfectant procedures used for viral, bacterial, and fungal pathogens such as alcohol, boiling, formalin, dry heat (<300°C), autoclaving at 121°C for 15 minutes, and ionizing, ultraviolet, or microwave radiation, are either ineffective or variably effective against aggregated prions.

The only means to ensure no risk of residual infectious prions is to use disposable materials. This is not always practical, as, for instance, a biosafety cabinet cannot be discarded if there is a CSF spill in the hood. Fortunately, there are several protocols considered sufficient for decontamination. For surfaces and heat-sensitive instruments, such as a biosafety cabinet, WHO recommends flooding the surface with 2N NaOH or undiluted NaClO, letting stand for 1 hour, mopping up, and rinsing with water. If the surface cannot tolerate NaOH or NaClO, thorough cleaning will remove most infectivity by dilution. Laboratories may derive some additional benefit by using one of the partially effective methods discussed previously. Non-disposable heat-resistant items preferably should be immersed in 1N NaOH, heated in a gravity displacement autoclave at 121°C for 30 min, cleaned and rinsed in water, then sterilized by routine methods. WHO has outlined several alternate decontamination methods. Using disposable cover sheets is one simple solution to avoid contaminating work surfaces and associated lengthy decontamination procedures.

With standard PPE—augmented by a few additional safety measures and prion-specific decontamination procedures—laboratories can safely manage biofluid testing in cases of prion disease.

 

The Microscopic World Inside Us  

Emerging Research Points to Microbiome’s Role in Health and Disease

Thousands of species of microbes—bacteria, viruses, fungi, and protozoa—inhabit every internal and external surface of the human body. Collectively, these microbes, known as the microbiome, outnumber the body’s human cells by about 10 to 1 and include more than 1,000 species of microorganisms and several million genes residing in the skin, respiratory system, urogenital, and gastrointestinal tracts. The microbiome’s complicated relationship with its human host is increasingly considered so crucial to health that researchers sometimes call it “the forgotten organ.”

Disturbances to the microbiome can arise from nutritional deficiencies, antibiotic use, and antiseptic modern life. Imbalances in the microbiome’s diverse microbial communities, which interact constantly with cells in the human body, may contribute to chronic health conditions, including diabetes, asthma and allergies, obesity and the metabolic syndrome, digestive disorders including irritable bowel syndrome (IBS), and autoimmune disorders like multiple sclerosis and rheumatoid arthritis, research shows.

While study of the microbiome is a growing research enterprise that has attracted enthusiastic media attention and venture capital, its findings are largely preliminary. But some laboratorians are already developing a greater appreciation for the microbiome’s contributions to human biochemistry and are considering a future in which they expect to measure changes in the microbiome to monitor disease and inform clinical practice.

Pivot Toward the Microbiome

Following the National Institutes of Health (NIH) Human Genome Project, many scientists noted the considerable genetic signal from microbes in the body and the existence of technology to analyze these microorganisms. That realization led NIH to establish the Human Microbiome Project in 2007, said Lita Proctor, PhD, its program director. In the project’s first phase, researchers studied healthy adults to produce a reference set of microbiomes and a resource of metagenomic sequences of bacteria in the airways, skin, oral cavities, and the gastrointestinal and vaginal tracts, plus a catalog of microbial genome sequences of reference strains. Researchers also evaluated specific diseases associated with disturbances in the microbiome, including gastrointestinal diseases such as Crohn’s disease, ulcerative colitis, IBS, and obesity, as well as urogenital conditions, those that involve the reproductive system, and skin diseases like eczema, psoriasis, and acne.

Phase 1 studies determined the composition of many parts of the microbiome, but did not define how that composition affects health or specific disease. The project’s second phase aims to “answer the question of what microbes actually do,” explained Proctor. Researchers are now examining properties of the microbiome including gene expression, protein, and human and microbial metabolite profiles in studies of pregnant women at risk for preterm birth, the gut hormones of patients at risk for IBS, and nasal microbiomes of patients at risk for type 2 diabetes.

Promising Lines of Research

Cystic fibrosis and microbiology investigator Michael Surette, PhD, sees promising microbiome research not just in terms of evidence of its effects on specific diseases, but also in what drives changes in the microbiome. Surette is Canada research chair in interdisciplinary microbiome research in the Farncombe Family Digestive Health Research Institute at McMaster University
in Hamilton, Ontario.

One type of study on factors driving microbiome change examines how alterations in composition and imbalances in individual patients relate to improving or worsening disease. “IBS, cystic fibrosis, and chronic obstructive pulmonary disease all have periods of instability or exacerbation,” he noted. Surette hopes that one day, tests will provide clinicians the ability to monitor changes in microbial composition over time and even predict when a patient’s condition is about to deteriorate. Monitoring perturbations to the gut microbiome might also help minimize collateral damage to the microbiome during aggressive antibiotic therapy for hospitalized patients, he added.

Monitoring changes to the microbiome also might be helpful for “culture negative” patients, who now may receive multiple, unsuccessful courses of different antibiotics that drive antibiotic resistance. Frustration with standard clinical biology diagnosis of lung infections in cystic fibrosis patients first sparked Surette’s investigations into the microbiome. He hopes that future tests involving the microbiome might also help asthma patients with neutrophilia, community-acquired pneumonia patients who harbor complex microbial lung communities lacking obvious pathogens, and hospitalized patients with pneumonia or sepsis. He envisions microbiome testing that would look for short-term changes indicating whether or not a drug is effective.

Companion Diagnostics

Daniel Peterson, MD, PhD, an assistant professor of pathology at Johns Hopkins University School of Medicine in Baltimore, believes the future of clinical testing involving the microbiome lies in companion diagnostics for novel treatments, and points to companies that are already developing and marketing tests that will require such assays.

Examples of microbiome-focused enterprises abound, including Genetic Analysis, based in Oslo, Norway, with its high-throughput test that uses 54 probes targeted to specific bacteria to measure intestinal gut flora imbalances in inflammatory bowel disease and irritable bowel syndrome patients. Paris, France-based Enterome is developing both novel drugs and companion diagnostics for microbiome-related diseases such as IBS and some metabolic diseases. Second Genome, based in South San Francisco, has developed an experimental drug, SGM-1019, that the company says blocks damaging activity of the microbiome in the intestine. Cambridge, Massachusetts-based Seres Therapeutics has received Food and Drug Administration orphan drug designation for SER-109, an oral therapeutic intended to correct microbial imbalances to prevent recurrent Clostridium difficile infection in adults.

One promising clinical use of the microbiome is fecal transplantation, which both prospective and retrospective studies have shown to be effective in patients with C. difficile infections who do not respond to front-line therapies, said James Versalovic, MD, PhD, director of Texas Children’s Hospital Microbiome Center and professor of pathology at Baylor College of Medicine in Houston. “Fecal transplants and other microbiome replacement strategies can radically change the composition of the microbiome in hours to days,” he explained.

But NIH’s Proctor discourages too much enthusiasm about fecal transplant. “Natural products like stool can have [side] effects,” she pointed out. “The [microbiome research] field needs to mature and we need to verify outcomes before anything becomes routine.”

Hurdles for Lab Testing

While he is hopeful that labs someday will use the microbiome to produce clinically useful information, Surette pointed to several problems that must be solved beforehand. First, molecular methods commonly used right now should be more quantitative and accurate. Additionally, research on the microbiome encompasses a wide variety of protocols, some of which are better at extracting particular types of bacteria and therefore can give biased views of communities living in the body. Also, tests may need to distinguish between dead and live microbes. Another hurdle is that labs using varied bioinfomatic methods may produce different results from the same sample, a problem that Surette sees as ripe for a solution from clinical laboratorians, who have expertise in standardizing robust protocols and in automating tests.

One way laboratorians can prepare for future, routine microbiome testing is to expand their notion of clinical chemistry to include both microbial and human biochemistry. “The line between microbiome science and clinical science is blurring,” said Versalovic. “When developing future assays to detect biochemical changes in disease states, we must consider the contributions of microbial metabolites and proteins and how to tailor tests to detect them.” In the future, clinical labs may test for uniquely microbial metabolites in various disease states, he predicted.

 

Automated Review of Mass Spectrometry Results  

Can We Achieve Autoverification?

Author: Katherine Alexander and Andrea R. Terrell, PhD  // Date: NOV.1.2015  // Source:Clinical Laboratory News

https://www.aacc.org/publications/cln/articles/2015/november/automated-review-of-mass-spectrometry-results-can-we-achieve-autoverification

 

Paralleling the upswing in prescription drug misuse, clinical laboratories are receiving more requests for mass spectrometry (MS) testing as physicians rely on its specificity to monitor patient compliance with prescription regimens. However, as volume has increased, reimbursement has declined, forcing toxicology laboratories both to increase capacity and lower their operational costs—without sacrificing quality or turnaround time. Now, new solutions are available enabling laboratories to bring automation to MS testing and helping them with the growing demand for toxicology and other testing.

What is the typical MS workflow?

A typical workflow includes a long list of manual steps. By the time a sample is loaded onto the mass spectrometer, it has been collected, logged into the lab information management system (LIMS), and prepared for analysis using a variety of wet chemistry techniques.

Most commercial clinical laboratories receive enough samples for MS analysis to batch analyze those samples. A batch consists of a calibrator(s), quality control (QC) samples, and patient/donor samples. Historically, the method would be selected (i.e. “analysis of opiates”), sample identification information would be entered manually into the MS software, and the instrument would begin analyzing each sample. Upon successful completion of the batch, the MS operator would view all of the analytical data, ensure the QC results were acceptable, and review each patient/donor specimen, looking at characteristics such as peak shape, ion ratios, retention time, and calculated concentration.

The operator would then post acceptable results into the LIMS manually or through an interface, and unacceptable results would be rescheduled or dealt with according to lab-specific protocols. In our laboratory we perform a final certification step for quality assurance by reviewing all information about the batch again, prior to releasing results for final reporting through the LIMS.

What problems are associated with this workflow?

The workflow described above results in too many highly trained chemists performing manual data entry and reviewing perfectly acceptable analytical results. Lab managers would prefer that MS operators and certifying scientists focus on troubleshooting problem samples rather than reviewing mounds of good data. Not only is the current process inefficient, it is mundane work prone to user errors. This risks fatigue, disengagement, and complacency by our highly skilled scientists.

Importantly, manual processes also take time. In most clinical lab environments, turnaround time is critical for patient care and industry competitiveness. Lab directors and managers are looking for solutions to automate mundane, error-prone tasks to save time and costs, reduce staff burnout, and maintain high levels of quality.

How can software automate data transfer from MS systems to LIMS?

Automation is not a new concept in the clinical lab. Labs have automated processes in shipping and receiving, sample preparation, liquid handling, and data delivery to the end user. As more labs implement MS, companies have begun to develop special software to automate data analysis and review workflows.

In July 2011, AIT Labs incorporated ASCENT into our workflow, eliminating the initial manual peak review step. ASCENT is an algorithm-based peak picking and data review system designed specifically for chromatographic data. The software employs robust statistical and modeling approaches to the raw instrument data to present the true signal, which often can be obscured by noise or matrix components.

The system also uses an exponentially modified Gaussian (EMG) equation to apply a best-fit model to integrated peaks through what is often a noisy signal. In our experience, applying the EMG results in cleaner data from what might appear to be poor chromatography ultimately allows us to reduce the number of samples we might otherwise rerun.

How do you validate the quality of results?

We’ve developed a robust validation protocol to ensure that results are, at minimum, equivalent to results from our manual review. We begin by building the assay in ASCENT, entering assay-specific information from our internal standard operating procedure (SOP). Once the assay is configured, validation proceeds with parallel batch processing to compare results between software-reviewed data and staff-reviewed data. For new implementations we run eight to nine batches of 30–40 samples each; when we are modifying or upgrading an existing implementation we run a smaller number of batches. The parallel batches should contain multiple positive and negative results for all analytes in the method, preferably spanning the analytical measurement range of the assay.

The next step is to compare the results and calculate the percent difference between the data review methods. We require that two-thirds of the automated results fall within 20% of the manually reviewed result. In addition to validating patient sample correlation, we also test numerous quality assurance rules that should initiate a flag for further review.

What are the biggest challenges during implementation and continual improvement initiatives?

On the technological side, our largest hurdle was loading the sequence files into ASCENT. We had created an in-house mechanism for our chemists to upload the 96-well plate map for their batch into the MS software. We had some difficulty transferring this information to ASCENT, but once we resolved this issue, the technical workflow proceeded fairly smoothly.

The greater challenge was changing our employees’ mindset from one of fear that automation would displace them, to a realization that learning this new technology would actually make them more valuable. Automating a non-mechanical process can be a difficult concept for hands-on scientists, so managers must be patient and help their employees understand that this kind of technology leverages the best attributes of software and people to create a powerful partnership.

We recommend that labs considering automated data analysis engage staff in the validation and implementation to spread the workload and the knowledge. As is true with most technology, it is best not to rely on just one or two super users. We also found it critical to add supervisor level controls on data file manipulation, such as removing a sample that wasn’t run from the sequence table. This can prevent inadvertent deletion of a file, requiring reinjection of the entire batch!

 

Understanding Fibroblast Growth Factor 23

Author: Damien Gruson, PhD  // Date: OCT.1.2015  // Source: Clinical Laboratory News

https://www.aacc.org/publications/cln/articles/2015/october/understanding-fibroblast-growth-factor-23

What is the relationship of FGF-23 to heart failure?

A Heart failure (HF) is an increasingly common syndrome associated with high morbidity, elevated hospital readmission rates, and high mortality. Improving diagnosis, prognosis, and treatment of HF requires a better understanding of its different sub-phenotypes. As researchers gained a comprehensive understanding of neurohormonal activation—one of the hallmarks of HF—they discovered several biomarkers, including natriuretic peptides, which now are playing an important role in sub-phenotyping HF and in driving more personalized management of this chronic condition.

Like the natriuretic peptides, fibroblast growth factor 23 (FGF-23) could become important in risk-stratifying and managing HF patients. Produced by osteocytes, FGF-23 is a key regulator of phosphorus homeostasis. It binds to renal and parathyroid FGF-Klotho receptor heterodimers, resulting in phosphate excretion, decreased 1-α-hydroxylation of 25-hydroxyvitamin D, and decreased parathyroid hormone (PTH) secretion. The relationship to PTH is important because impaired homeostasis of cations and decreased glomerular filtration rate might contribute to the rise of FGF-23. The amino-terminal portion of FGF-23 (amino acids 1-24) serves as a signal peptide allowing secretion into the blood, and the carboxyl-terminal portion (aa 180-251) participates in its biological action.

How might FGF-23 improve HF risk assessment?

Studies have shown that FGF-23 is related to the risk of cardiovascular diseases and mortality. It was first demonstrated that FGF-23 levels were independently associated with left ventricular mass index and hypertrophy as well as mortality in patients with chronic kidney disease (CKD). FGF-23 also has been associated with left ventricular dysfunction and atrial fibrillation in coronary artery disease subjects, even in the absence of impaired renal function.

FGF-23 and FGF receptors are both expressed in the myocardium. It is possible that FGF-23 has direct effects on the heart and participates in the physiopathology of cardiovascular diseases and HF. Experiments have shown that for in vitro cultured rat cardiomyocytes, FGF-23 stimulates pathological hypertrophy by activating the calcineurin-NFAT pathway—and in wild-type mice—the intra-myocardial or intravenous injection of FGF-23 resulted in left ventricular hypertrophy. As such, FGF-23 appears to be a potential stimulus of myocardial hypertrophy, and increased levels may contribute to the worsening of heart failure and long-term cardiovascular death.

Researchers have documented that HF patients have elevated FGF-23 circulating levels. They have also found a significant correlation between plasma levels of FGF-23 and B-type natriuretic peptide, a biomarker related to ventricular stretch and cardiac hypertrophy, in patients with left ventricular hypertrophy. As such, measuring FGF-23 levels might be a useful tool to predict long-term adverse cardiovascular events in HF patients.

Interestingly, researchers have documented a significant relationship between FGF-23 and PTH in both CKD and HF patients. As PTH stimulates FGF-23 expression, it could be that in HF patients, increased PTH levels increase the bone expression of FGF-23, which enhances its effects on the heart.

 

The Past, Present, and Future of Western Blotting in the Clinical Laboratory

Author: Curtis Balmer, PhD  // Date: OCT.1.2015  // Source: Clinical Laboratory News

https://www.aacc.org/publications/cln/articles/2015/october/the-past-present-and-future-of-western-blotting-in-the-clinical-laboratory

Much of the discussion about Western blotting centers around its performance as a biological research tool. This isn’t surprising. Since its introduction in the late 1970s, the Western blot has been adopted by biology labs of virtually every stripe, and become one of the most widely used techniques in the research armamentarium. However, Western blotting has also been employed in clinical laboratories to aid in the diagnosis of various diseases and disorders—an equally important and valuable application. Yet there has been relatively little discussion of its use in this context, or of how advances in Western blotting might affect its future clinical use.

Highlighting the clinical value of Western blotting, Stanley Naides, MD, medical director of Immunology at Quest Diagnostics observed that, “Western blotting has been a very powerful tool in the laboratory and for clinical diagnosis. It’s one of many various methods that the laboratorian brings to aid the clinician in the diagnosis of disease, and the selection and monitoring of therapy.” Indeed, Western blotting has been used at one time or the other to aid in the diagnosis of infectious diseases including hepatitis C (HCV), HIV, Lyme disease, and syphilis, as well as autoimmune disorders such as paraneoplastic disease and myositis conditions.

However, Naides was quick to point out that the choice of assays to use clinically is based on their demonstrated sensitivity and performance, and that the search for something better is never-ending. “We’re constantly looking for methods that improve detection of our target [protein],” Naides said. “There have been a number of instances where we’ve moved away from Western blotting because another method proves to be more sensitive.” But this search can also lead back to Western blotting. “We’ve gone away from other methods because there’s been a Western blot that’s been developed that’s more sensitive and specific. There’s that constant movement between methods as new tests are developed.”

In recent years, this quest has been leading clinical laboratories away from Western blotting toward more sensitive and specific diagnostic assays, at least for some diseases. Using confirmatory diagnosis of HCV infection as an example, Sai Patibandla, PhD, director of the immunoassay group at Siemens Healthcare Diagnostics, explained that movement away from Western blotting for confirmatory diagnosis of HCV infection began with a technical modification called Recombinant Immunoblotting Assay (RIBA). RIBA streamlines the conventional Western blot protocol by spotting recombinant antigen onto strips which are used to screen patient samples for antibodies against HCV. This approach eliminates the need to separate proteins and transfer them onto a membrane.

The RIBA HCV assay was initially manufactured by Chiron Corporation (acquired by Novartics Vaccines and Diagnostics in 2006). It received Food and Drug Administration (FDA) approval in 1999, and was marketed as Chiron RIBA HCV 3.0 Strip Immunoblot Assay. Patibandla explained that, at the time, the Chiron assay “…was the only FDA-approved confirmatory testing for HCV.” In 2013 the assay was discontinued and withdrawn from the market due to reports that it was producing false-positive results.

Since then, clinical laboratories have continued to move away from Western blot-based assays for confirmation of HCV in favor of the more sensitive technique of nucleic acid testing (NAT). “The migration is toward NAT for confirmation of HCV [diagnosis]. We don’t use immunoblots anymore. We don’t even have a blot now to confirm HCV,” Patibandla said.

Confirming HIV infection has followed a similar path. Indeed, in 2014 the Centers for Disease Control and Prevention issued updated recommendations for HIV testing that, in part, replaced Western blotting with NAT. This change was in response to the recognition that the HIV-1 Western blot assay was producing false-negative or indeterminable results early in the course of HIV infection.

At this juncture it is difficult to predict if this trend away from Western blotting in clinical laboratories will continue. One thing that is certain, however, is that clinicians and laboratorians are infinitely pragmatic, and will eagerly replace current techniques with ones shown to be more sensitive, specific, and effective. This raises the question of whether any of the many efforts currently underway to improve Western blotting will produce an assay that exceeds the sensitivity of currently employed techniques such as NAT.

Some of the most exciting and groundbreaking work in this area is being done by Amy Herr, PhD, a professor of bioengineering at University of California, Berkeley. Herr’s group has taken on some of the most challenging limitations of Western blotting, and is developing techniques that could revolutionize the assay. For example, the Western blot is semi-quantitative at best. This weakness dramatically limits the types of answers it can provide about changes in protein concentrations under various conditions.

To make Western blotting more quantitative, Herr’s group is, among other things, identifying losses of protein sample mass during the assay protocol. About this, Herr explains that the conventional Western blot is an “open system” that involves lots of handling of assay materials, buffers, and reagents that makes it difficult to account for protein losses. Or, as Kevin Lowitz, a senior product manager at Thermo Fisher Scientific, described it, “Western blot is a [simple] technique, but a really laborious one, and there are just so many steps and so many opportunities to mess it up.”

Herr’s approach is to reduce the open aspects of Western blot. “We’ve been developing these more closed systems that allow us at each stage of the assay to account for [protein mass] losses. We can’t do this exactly for every target of interest, but it gives us a really good handle [on protein mass losses],” she said. One of the major mechanisms Herr’s lab is using to accomplish this is to secure proteins to the blot matrix with covalent bonding rather than with the much weaker hydrophobic interactions that typically keep the proteins in place on the membrane.

Herr’s group also has been developing microfluidic platforms that allow Western blotting to be done on single cells, “In our system we’re doing thousands of independent Westerns on single cells in four hours. And, hopefully, we’ll cut that down to one hour over the next couple years.”

Other exciting modifications that stand to dramatically increase the sensitivity, quantitation, and through-put of Western blotting also are being developed and explored. For example, the use of capillary electrophoresis—in which proteins are conveyed through a small electrolyte-filled tube and separated according to size and charge before being dropped onto a blotting membrane—dramatically reduces the amount of protein required for Western blot analysis, and thereby allows Westerns to be run on proteins from rare cells or for which quantities of sample are extremely limited.

Jillian Silva, PhD, an associate specialist at the University of California, San Francisco Helen Diller Family Comprehensive Cancer Center, explained that advances in detection are also extending the capabilities of Western blotting. “With the advent of fluorescence detection we have a way to quantitate Westerns, and it is now more quantitative than it’s ever been,” said Silva.

Whether or not these advances produce an assay that is adopted by clinical laboratories remains to be seen. The emphasis on Western blotting as a research rather than a clinical tool may bias advances in favor of the needs and priorities of researchers rather than clinicians, and as Patibandla pointed out, “In the research world Western blotting has a certain purpose. [Researchers] are always coming up with new things, and are trying to nail down new proteins, so you cannot take Western blotting away.” In contrast, she suggested that for now, clinical uses of Western blotting remain “limited.”

 

Adapting Next Generation Technologies to Clinical Molecular Oncology Service

Author: Ronald Carter, PhD, DVM  // Date: OCT.1.2015  // Source: Clinical Laboratory News

https://www.aacc.org/publications/cln/articles/2015/october/adapting-next-generation-technologies-to-clinical-molecular-oncology-service

Next generation technologies (NGT) deliver huge improvements in cost efficiency, accuracy, robustness, and in the amount of information they provide. Microarrays, high-throughput sequencing platforms, digital droplet PCR, and other technologies all offer unique combinations of desirable performance.

As stronger evidence of genetic testing’s clinical utility influences patterns of patient care, demand for NGT testing is increasing. This presents several challenges to clinical laboratories, including increased urgency, clinical importance, and breadth of application in molecular oncology, as well as more integration of genetic tests into synoptic reporting. Laboratories need to add NGT-based protocols while still providing old tests, and the pace of change is increasing.What follows is one viewpoint on the major challenges in adopting NGTs into diagnostic molecular oncology service.

Choosing a Platform

Instrument selection is a critical decision that has to align with intended test applications, sequencing chemistries, and analytical software. Although multiple platforms are available, a mainstream standard has not emerged. Depending on their goals, laboratories might set up NGTs for improved accuracy of mutation detection, massively higher sequencing capacity per test, massively more targets combined in one test (multiplexing), greater range in sequencing read length, much lower cost per base pair assessed, and economy of specimen volume.

When high-throughput instruments first made their appearance, laboratories paid more attention to the accuracy of base-reading: Less accurate sequencing meant more data cleaning and resequencing (1). Now, new instrument designs have narrowed the differences, and test chemistry can have a comparatively large impact on analytical accuracy (Figure 1). The robustness of technical performance can also vary significantly depending upon specimen type. For example, LifeTechnologies’ sequencing platforms appear to be comparatively more tolerant of low DNA quality and concentration, which is an important consideration for fixed and processed tissues.

https://www.aacc.org/~/media/images/cln/articles/2015/october/carter_fig1_cln_oct15_ed.jpg

Figure 1 Comparison of Sequencing Chemistries

Sequence pile-ups of the same target sequence (2 large genes), all performed on the same analytical instrument. Results from 4 different chemistries, as designed and supplied by reagent manufacturers prior to optimization in the laboratory. Red lines represent limits of exons. Height of blue columns proportional to depth of coverage. In this case, the intent of the test design was to provide high depth of coverage so that reflex Sanger sequencing would not be necessary. Courtesy B. Sadikovic, U. of Western Ontario.

 

In addition, batching, robotics, workload volume patterns, maintenance contracts, software licenses, and platform lifetime affect the cost per analyte and per specimen considerably. Royalties and reagent contracts also factor into the cost of operating NGT: In some applications, fees for intellectual property can represent more than 50% of the bench cost of performing a given test, and increase substantially without warning.

Laboratories must also deal with the problem of obsolescence. Investing in a new platform brings the angst of knowing that better machines and chemistries are just around the corner. Laboratories are buying bigger pieces of equipment with shorter service lives. Before NGTs, major instruments could confidently be expected to remain current for at least 6 to 8 years. Now, a major instrument is obsolete much sooner, often within 2 to 3 years. This means that keeping it in service might cost more than investing in a new platform. Lease-purchase arrangements help mitigate year-to-year fluctuations in capital equipment costs, and maximize the value of old equipment at resale.

One Size Still Does Not Fit All

Laboratories face numerous technical considerations to optimize sequencing protocols, but the test has to be matched to the performance criteria needed for the clinical indication (2). For example, measuring response to treatment depends first upon the diagnostic recognition of mutation(s) in the tumor clone; the marker(s) then have to be quantifiable and indicative of tumor volume throughout the course of disease (Table 1).

As a result, diagnostic tests need to cover many different potential mutations, yet accurately identify any clinically relevant mutations actually present. On the other hand, tests for residual disease need to provide standardized, sensitive, and accurate quantification of a selected marker mutation against the normal background. A diagnostic panel might need 1% to 3% sensitivity across many different mutations. But quantifying early response to induction—and later assessment of minimal residual disease—needs a test that is reliably accurate to the 10-4 or 10-5 range for a specific analyte.

Covering all types of mutations in one diagnostic test is not yet possible. For example, subtyping of acute myeloid leukemia is both old school (karyotype, fluorescent in situ hybridization, and/or PCR-based or array-based testing for fusion rearrangements, deletions, and segmental gains) and new school (NGT-based panel testing for molecular mutations).

Chemistries that cover both structural variants and copy number variants are not yet in general use, but the advantages of NGTs compared to traditional methods are becoming clearer, such as in colorectal cancer (3). Researchers are also using cell-free DNA (cfDNA) to quantify residual disease and detect resistance mutations (4). Once a clinically significant clone is identified, enrichment techniques help enable extremely sensitive quantification of residual disease (5).

Validation and Quality Assurance

Beyond choosing a platform, two distinct challenges arise in bringing NGTs into the lab. The first is assembling the resources for validation and quality assurance. The second is keeping tests up-to-date as new analytes are needed. Even if a given test chemistry has the flexibility to add analytes without revalidating the entire panel, keeping up with clinical advances is a constant priority.

Due to their throughput and multiplexing capacities, NGT platforms typically require considerable upfront investment to adopt, and training staff to perform testing takes even more time. Proper validation is harder to document: Assembling positive controls, documenting test performance criteria, developing quality assurance protocols, and conducting proficiency testing are all demanding. Labs meet these challenges in different ways. Laboratory-developed tests (LDTs) allow self-determined choice in design, innovation, and control of the test protocol, but can be very expensive to set up.

Food and Drug Administration (FDA)-approved methods are attractive but not always an option. More FDA-approved methods will be marketed, but FDA approval itself brings other trade-offs. There is a cost premium compared to LDTs, and the test methodologies are locked down and not modifiable. This is particularly frustrating for NGTs, which have the specific attraction of extensive multiplexing capacity and accommodating new analytes.

IT and the Evolution of Molecular Oncology Reporting Standards

The options for information technology (IT) pipelines for NGTs are improving rapidly. At the same time, recent studies still show significant inconsistencies and lack of reproducibility when it comes to interpreting variants in array comparative genomic hybridization, panel testing, tumor expression profiling, and tumor genome sequencing. It can be difficult to duplicate published performances in clinical studies because of a lack of sufficient information about the protocol (chemistry) and software. Building bioinformatics capacity is a key requirement, yet skilled people are in short supply and the qualifications needed to work as a bioinformatician in a clinical service are not yet clearly defined.

Tumor biology brings another level of complexity. Bioinformatic analysis must distinguish tumor-specific­ variants from genomic variants. Sequencing of paired normal tissue is often performed as a control, but virtual normal controls may have intriguing advantages (6). One of the biggest challenges is to reproducibly interpret the clinical significance of interactions between different mutations, even with commonly known, well-defined mutations (7). For multiple analyte panels, such as predictive testing for breast cancer, only the performance of the whole panel in a population of patients can be compared; individual patients may be scored into different risk categories by different tests, all for the same test indication.

In large scale sequencing of tumor genomes, which types of mutations are most informative in detecting, quantifying, and predicting the behavior of the tumor over time? The amount and complexity of mutation varies considerably across different tumor types, and while some mutations are more common, stable, and clinically informative than others, the utility of a given tumor marker varies in different clinical situations. And, for a given tumor, treatment effect and metastasis leads to retesting for changes in drug sensitivities.

These complexities mean that IT must be designed into the process from the beginning. Like robotics, IT represents a major ancillary decision. One approach many labs choose is licensed technologies with shared databases that are updated in real time. These are attractive, despite their cost and licensing fees. New tests that incorporate proprietary IT with NGT platforms link the genetic signatures of tumors to clinically significant considerations like tumor classification, recommended methodologies for monitoring response, predicted drug sensitivities, eligible clinical trials, and prognostic classifications. In-house development of such solutions will be difficult, so licensing platforms from commercial partners is more likely to be the norm.

The Commercial Value of Health Records and Test Data

The future of cancer management likely rests on large-scale databases that link hereditary and somatic tumor testing with clinical outcomes. Multiple centers have such large studies underway, and data extraction and analysis is providing increasingly refined interpretations of clinical significance.

Extracting health outcomes to correlate with molecular test results is commercially valuable, as the pharmaceutical, insurance, and healthcare sectors focus on companion diagnostics, precision medicine, and evidence-based health technology assessment. Laboratories that can develop tests based on large-scale integration of test results to clinical utility will have an advantage.

NGTs do offer opportunities for net reductions in the cost of healthcare. But the lag between availability of a test and peer-evaluated demon­stration of clinical utility can be considerable. Technical developments arise faster than evidence of clinical utility. For example, immuno­histochemistry, estrogen receptor/progesterone receptor status, HER2/neu, and histology are still the major pathological criteria for prognostic evaluation of breast cancer at diagnosis, even though multiple analyte tumor profiling has been described for more than 15 years. Healthcare systems need a more concerted assessment of clinical utility if they are to take advantage of the promises of NGTs in cancer care.

Disruptive Advances

Without a doubt, “disruptive” is an appropriate buzzword in molecular oncology, and new technical advances are about to change how, where, and for whom testing is performed.

• Predictive Testing

Besides cost per analyte, one of the drivers for taking up new technologies is that they enable multiplexing many more analytes with less biopsy material. Single-analyte sequential testing for epidermal growth factor receptor (EGFR), anaplastic lymphoma kinase, and other targets on small biopsies is not sustainable when many more analytes are needed, and even now, a significant proportion of test requests cannot be completed due to lack of suitable biopsy material. Large panels incorporating all the mutations needed to cover multiple tumor types are replacing individual tests in companion diagnostics.

• Cell-Free Tumor DNA

Challenges of cfDNA include standardizing the collection and processing methodologies, timing sampling to minimize the effect of therapeutic toxicity on analytical accuracy, and identifying the most informative sample (DNA, RNA, or protein). But for more and more tumor types, it will be possible to differentiate benign versus malignant lesions, perform molecular subtyping, predict response, monitor treatment, or screen for early detection—all without a surgical biopsy.

cfDNA technologies can also be integrated into core laboratory instrumentation. For example, blood-based EGFR analysis for lung cancer is being developed on the Roche cobas 4800 platform, which will be a significant change from the current standard of testing based upon single tests of DNA extracted from formalin-fixed, paraffin-embedded sections selected by a pathologist (8).

• Whole Genome and Whole Exome Sequencing

Whole genome and whole exome tumor sequencing approaches provide a wealth of biologically important information, and will replace individual or multiple gene test panels as the technical cost of sequencing declines and interpretive accuracy improves (9). Laboratories can apply informatics selectively or broadly to extract much more information at relatively little increase in cost, and the interpretation of individual analytes will be improved by the context of the whole sequence.

• Minimal Residual Disease Testing

Massive resequencing and enrichment techniques can be used to detect minimal residual disease, and will provide an alternative to flow cytometry as costs decline. The challenge is to develop robust analytical platforms that can reliably produce results in a high proportion of patients with a given tumor type, despite using post-treatment specimens with therapy-induced degradation, and a very low proportion of target (tumor) sequence to benign background sequence.

The tumor markers should remain informative for the burden of disease despite clonal evolution over the course of multiple samples taken during progression of the clinical course and treatment. Quantification needs to be accurate and sensitive down to the 10-5 range, and cost competitive with flow cytometry.

• Point-of-Care Test Methodologies

Small, rapid, cheap, and single use point-of-care (POC) sequencing devices are coming. Some can multiplex with analytical times as short as 20 minutes. Accurate and timely testing will be possible in places like pharmacies, oncology clinics, patient service centers, and outreach programs. Whether physicians will trust and act on POC results alone, or will require confirmation by traditional laboratory-based testing, remains to be seen. However, in the simplest type of application, such as a patient known to have a particular mutation, the advantages of POC-based testing to quantify residual tumor burden are clear.

Conclusion

Molecular oncology is moving rapidly from an esoteric niche of diagnostics to a mainstream, required component of integrated clinical laboratory services. While NGTs are markedly reducing the cost per analyte and per specimen, and will certainly broaden the scope and volume of testing performed, the resources required to choose, install, and validate these new technologies are daunting for smaller labs. More rapid obsolescence and increased regulatory scrutiny for LDTs also present significant challenges. Aligning test capacity with approved clinical indications will require careful and constant attention to ensure competitiveness.

References

1. Liu L, Li Y, Li S, et al. Comparison of next-generation sequencing systems. J Biomed Biotechnol 2012; doi:10.1155/2012/251364.

2. Brownstein CA, Beggs AH, Homer N, et al. An international effort towards developing standards for best practices in analysis, interpretation and reporting of clinical genome sequencing results in the CLARITY Challenge. Genome Biol 2014;15:R53.

3. Haley L, Tseng LH, Zheng G, et al. Performance characteristics of next-generation sequencing in clinical mutation detection of colorectal ­cancers. [Epub ahead of print] Modern Pathol July 31, 2015 as doi:10.1038/modpathol.2015.86.

4. Butler TM, Johnson-Camacho K, Peto M, et al. Exome sequencing of cell-free DNA from metastatic cancer patients identifies clinically actionable mutations distinct from primary ­disease. PLoS One 2015;10:e0136407.

5. Castellanos-Rizaldos E, Milbury CA, Guha M, et al. COLD-PCR enriches low-level variant DNA sequences and increases the sensitivity of genetic testing. Methods Mol Biol 2014;1102:623–39.

6. Hiltemann S, Jenster G, Trapman J, et al. Discriminating somatic and germline mutations in tumor DNA samples without matching normals. Genome Res 2015;25:1382–90.

7. Lammers PE, Lovly CM, Horn L. A patient with metastatic lung adenocarcinoma harboring concurrent EGFR L858R, EGFR germline T790M, and PIK3CA mutations: The challenge of interpreting results of comprehensive mutational testing in lung cancer. J Natl Compr Canc Netw 2015;12:6–11.

8. Weber B, Meldgaard P, Hager H, et al. Detection of EGFR mutations in plasma and biopsies from non-small cell lung cancer patients by allele-specific PCR assays. BMC Cancer 2014;14:294.

9. Vogelstein B, Papadopoulos N, Velculescu VE, et al. Cancer genome landscapes. Science 2013;339:1546–58.

10. Heitzer E, Auer M, Gasch C, et al. Complex tumor genomes inferred from single circulating tumor cells by array-CGH and next-generation sequencing. Cancer Res 2013;73:2965–75.

11. Healy B. BRCA genes — Bookmaking, fortunetelling, and medical care. N Engl J Med 1997;336:1448–9.

 

 

 

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Excess Eating, Overweight, and Diabetic

Larry H Bernstein, MD, FCAP, Curator

LPBI

 

You Did NOT Eat Your Way to Diabetes!

http://www.phlaunt.com/diabetes/14046739.php

 

The myth that diabetes is caused by overeating also hurts the one out of five people who are not overweight when they contract Type 2 Diabetes. Because doctors only think “Diabetes” when they see a patient who fits the stereotype–the grossly obese inactive patient–they often neglect to check people of normal weight for blood sugar disorders even when they show up with classic symptoms of high blood sugar such as recurrent urinary tract infections or neuropathy.

Where Did This Toxic Myth Come From?

The way this myth originated is this: Because people with Type 2 Diabetes are often overweight and because many people who are overweight have a syndrome called “insulin resistance” in which their cells do not respond properly to insulin so that they require larger than normal amounts of insulin to lower their blood sugar, the conclusion was drawn years ago that insulin resistance was the cause of Type 2 Diabetes.

It made sense. Something was burning out the beta cells in these people, and it seemed logical that the something must be the stress of pumping out huge amounts of insulin, day after day. This idea was so compelling that it was widely believed by medical professionals, though few realized it had never been subjected to careful investigation by large-scale research.

That is why any time there is an article in the news about Type 2 Diabetes you are likely to read something that says, “While Type 1 diabetes (sometimes called Juvenile Diabetes) is a condition where the body does not produce insulin, Type 2 Diabetes is the opposite: a condition where the body produces far too much insulin because of insulin resistance caused by obesity.”

When your doctor tells you the same thing, the conclusion is inescapable: your overeating caused you to put on excess fat and that your excess fat is what made you diabetic.

Blaming the Victim

This line of reasoning leads to subtle, often unexpressed, judgmental decisions on the part of your doctor, who is likely to believe that had you not been such a pig, you would not have given yourself this unnecessary disease.

And because of this unspoken bias, unless you are able to “please” your doctor by losing a great deal of weight after your diagnosis you may find yourself treated with a subtle but callous disregard because of the doctor’s feeling that you brought this condition down on yourself. This bias is similar to that held by doctors who face patients who smoke a pack a day and get lung cancer and still refuse to stop smoking.

You also see this bias frequently expressed in the media. Articles on the “obesity epidemic” blame overeating for a huge increase in the number of people with diabetes, including children and teenagers who are pictured greedily gorging on supersized fast foods while doing no exercise more strenuous than channel surfing. In a society where the concepts “thin” and “healthy” have taken on the overtones of moral virtue and where the only one of the seven deadly sins that still inspires horror and condemnation is gluttony, being fat is considered by many as sure proof of moral weakness. So it is not surprising that the subtext of media coverage of obesity and diabetes is that diabetes is nothing less than the just punishment you deserve for being such a glutton.

Except that it’s not true.

Obesity Has Risen Dramatically While Diabetes Rates Have Not

The rate of obesity has grown alarmingly over the past decades, especially in certain regions of the U.S. The NIH reports that “From 1960-2 to 2005-6, the prevalence of obesity increased from 13.4 to 35.1 percent in U.S. adults age 20 to 74.7.”

If obesity was causing diabetes, you’d exect to see a similar rise in the diabetes rate. But this has not happened. The CDC reports that “From 1980 through 2010, the crude prevalence of diagnosed diabetes increased …from 2.5% to 6.9%.” However, if you look at the graph that accompanies this statement, you see that the rate of diabetes diagnoses rose only gradually through this period–to about 3.5% until it suddenly sped upward in the late 1990s. This sudden increase largely due to the fact that in 1998 the American Diabetes Association changed the criteria by which diabetes was to be diagnosed, lowering the fasting blood sugar level used to diagnose diabetes from 141 mg/dl to 126 mg/dl. (Details HERE)

Analyzing these statistics, it becomes clear that though roughtly 65 million more Americans became fat over this period, only 13 million more Americans became diabetic.

And to further confuse the matter, several factors other than the rise in obesity and the ADA’s lowering of the diagnostic cutoff also came into play during this period which also raised the rate of diabetes diagnoses:

Diabetes becomes more common as people age as the pancreas like other organs, becames less efficient. In 1950 only 12% of the U.S. population was over 65. By 2010 40% was, and of those 40%, 19% were over 75.(Details HERE.)

At the same time, the period during which the rate of diabetes rose was also the period in which doctors began to heavily prescribe statins, a class of drugs we now know raises the risk of developing diabetes. (Details HERE.)

Why Obesity Doesn’t Cause Diabetes: The Genetic Basis of Diabetes

While people who have diabetes are often heavy, one out of five people diagnosed with diabetes are thin or normal weight. And though heavy people with diabetes are, indeed, likely to be insulin resistant, the majority of people who are overweight will never develop diabetes. In fact, they will not develop diabetes though they are likely to be just as insulin resistant as those who do–or even more so.

The message that diabetes researchers in academic laboratories are coming up with about what really causes diabetes is quite different from what you read in the media. What they are finding is that to get Type 2 Diabetes you need to have some combination of a variety of already-identified genetic flaws which produce the syndrome that we call Type 2 Diabetes. This means that unless you have inherited abnormal genes or had your genes damaged by exposure to pesticides, plastics and other environmental toxins known to cause genetic damage, you can eat until you drop and never develop diabetes.

Now let’s look in more depth at what peer reviewed research has found about the true causes of diabetes

Twin Studies Back up a Genetic Cause for Diabetes

Studies of identical twins showed that twins have an 80% concordance for Type 2 Diabetes. In other words, if one twin has Type 2 Diabetes, the chance that the other will have it two are 4 out of 5. While you might assume that this might simply point to the fact that twins are raised in the same home by mothers who feed them the same unhealthy diets, studies of non-identical twins found NO such correlation. The chances that one non-identical twin might have Type 2 Diabetes if the other had it were much lower, though these non-identical twins, born at the same time and raised by the same caregivers were presumably also exposed to the same unhealthy diets.

This kind of finding begins to hint that there is more than just bad habits to blame for diabetes. A high concordance between identical twins which is not shared by non-identical twins is usually advanced as an argument for a genetic cause, though because one in five identical twins did not become diabetic, it is assumed that some additional factors beyond the inherited genome must come into play to cause the disease to appear. Often this factor is an exposure to an environmental toxin which knocks out some other, protective genetic factor.

The Genetic Basis of Type 2 Diabetes Mellitus: Impaired Insulin Secretion versus Impaired Insulin Sensitivity. John E. Gerich. Endocrine Reviews 19(4) 491-503, 1998.

The List of Genes Associated with Type 2 Keeps Growing

Here is a brief list of some of the abnormal genes that have been found to be associated with Type 2 Diabetes in people of European extraction: TCF7L2, HNF4-a, PTPN, SHIP2, ENPP1, PPARG, FTO, KCNJ11, NOTCh3, WFS1, CDKAL1, IGF2BP2, SLC30A8, JAZF1, and HHEX.

People from non-European ethnic groups have been found to have entirely different sets of diabetic genes than do Western Europeans, like the UCP2 polymorphism found in Pima Indians and the three Calpain-10 gene polymorphisms that have been found to be associated with diabetes in Mexicans. The presence of a variation in yet another gene, SLC16A11, was recently found to be associated with a 25% higher risk of a Mexican developing Type 2 diabetes.

The More Diabetes Genes You Have The Worse Your Beta Cells Perform

A study published in the Journal Diabetologia in November 2008 studied how well the beta cells secreted insulin in 1,211 non-diabetic individuals. They then screened these people for abnormalities in seven genes that have been found associated with Type 2 Diabetes.

They found that with each abnormal gene found in a person’s genome, there was an additive effect on that person’s beta cell dysfunction with each additional gene causing poorer beta cell function.

The impact of these genetic flaws becomes clear when we learn that in these people who were believed to be normal, beta cell glucose sensitivity and insulin production at meal times was decreased by 39% in people who had abnormalities in five genes. That’s almost half. And if your beta cells are only putting out half as much insulin as a normal person’s it takes a lot less stress on those cells to push you into becoming diabetic.

Beta cell glucose sensitivity is decreased by 39% in non-diabetic individuals carrying multiple diabetes-risk alleles compared with those with no risk alleles L. Pascoe et al. Diabetologia, Volume 51, Number 11 / November, 2008.

Gene Tests Predict Diabetes Independent of Conventional “Risk Factors”

A study of 16,061 Swedish and 2770 Finnish subjects found that

Variants in 11 genes (TCF7L2, PPARG, FTO, KCNJ11, NOTCh3, WFS1, CDKAL1, IGF2BP2, SLC30A8, JAZF1, and HHEX) were significantly associated with the risk of Type 2 Diabetes independently of clinical risk factors [i.e. family history, obesity etc.]; variants in 8 of these genes were associated with impaired beta-cell function.

Note that though the subjects here were being screened for Type 2 Diabetes, the defect found here was NOT insulin resistance, but rather deficient insulin secretion. This study also found that:

The discriminative power of genetic risk factors improved with an increasing duration of follow-up, whereas that of clinical risk factors decreased.

In short, the longer these people were studied, the more likely the people with these gene defects were to develop diabetes.

Clinical Risk Factors, DNA Variants, and the Development of Type 2 Diabetes Valeriya Lyssenko, M.D. et. al. New England Journal of Medicine, Volume 359:2220-2232, November 20, 2008,Number 21.

What A Common Diabetes Gene Does

A study published in July of 2009 sheds light on what exactly it is that an allele (gene variant) often found associated with diabetes does. The allele in question is one of TCF7L2 transcription factor gene. The study involved 81 normal healthy young Danish men whose genes were tested. They were then given a battery of tests to examine their glucose metabolisms. The researchers found that:

Carriers of the T allele were characterised by reduced 24 h insulin concentrations … and reduced insulin secretion relative to glucose during a mixed meal test … but not during an IVGTT [intravenous glucose tolerance test].

This is an interesting finding, because what damages our bodies is the blood sugar we experience after eating “a mixed meal” but so much research uses the artificial glucose tolerance (GTT) test to assess blood sugar health. This result suggests that the GTT may be missing important signs of early blood sugar dysfunction and that the mixed meal test may be a better diagnostic test than the GTT. I have long believed this to be true, since so many people experience reactive lows when they take the GTT which produces a seemingly “normal reading” though they routinely experience highs after eating meals. These highs are what damage our organs.

Young men with the TCF7L2 allele also responded with weak insulin secretion in response to the incretin hormone GLP-1 and “Despite elevated hepatic [liver] glucose production, carriers of the T allele had significantly reduced 24 h glucagon concentrations … suggesting altered alpha cell function.”

Here again we see evidence that long before obesity develops, people with this common diabetes gene variant show highly abnormal blood sugar behavior. Abnormal production of glucose by the liver may also contribute to obesity as metformin, a drug that that blocks the liver’s production of glucose blocks weight gain and often causes weight loss.

The T allele of rs7903146 TCF7L2 is associated with impaired insulinotropic action of incretin hormones, reduced 24 h profiles of plasma insulin and glucagon, and increased hepatic glucose production in young healthy men. K. Pilgaard et al. Diabetologia, Issue Volume 52, Number 7 / July, 2009. DOI 10.1007/s00125-009-1307-x

Genes Linked to African Heritage Linked to Poor Carbohydrate Metabolism

It has long been known that African-Americans have a much higher rate of diabetes and metabolic syndrome than the American population as a whole. This has been blamed on lifestyle, but a 2009 genetic study finds strong evidence that the problem is genetic.

The study reports,

Using genetic samples obtained from a cohort of subjects undergoing cardiac-related evaluation, a strict algorithm that filtered for genomic features at multiple levels identified 151 differentially-expressed genes between Americans of African ancestry and those of European ancestry. Many of the genes identified were associated with glucose and simple sugar metabolism, suggestive of a model whereby selective adaptation to the nutritional environment differs between populations of humans separated geographically over time.

In the full text discussion the authors state,

These results suggest that differences in glucose metabolism between Americans of African and European may reside at the transcriptional level. The down-regulation of these genes in the AA cohorts argues against these changes being a compensatory response to hyperglycemia and suggests instead a genetic adaptation to changes in the availability of dietary sugars that may no longer be appropriate to a Western Diet.

In conclusion the authors note that the vegetarian diet of the Seventh Day Adventists, often touted as proof of the usefulness of the “Diet Pyramid” doesn’t provide the touted health benefits to people of African American Heritage. Obviously, when hundreds of carbohydrate metabolizing genes aren’t working properly the diet needed is a low carbohydrate diet.

The study is available in full text here:

Stable Patterns of Gene Expression Regulating Carbohydrate Metabolism Determined by Geographic AncestryJonathan C. Schisler et. al. PLoS One 4(12): e8183. doi:10.1371/journal.pone.0008183

Gene that Disrupts Circadian Clock Associated with Type 2 Diabetes

It has been known for a while that people who suffer from sleep disturbances often suffer raised insulin resistance. In December of 2008, researchers identified a gene, “rs1387153, near MTNR1B (which encodes the melatonin receptor 2 (MT2)), as a modulator of fasting plasma glucose.” They conclude,

Our data suggest a possible link between circadian rhythm regulation and glucose homeostasis through the melatonin signaling pathway.

Melatonin levels appear to control the body clock which, in turn, regulates the secretion of substances that modify blood pressure, hormone levels, insulin secretion and many other processes throughout the body.

A variant near MTNR1B is associated with increased fasting plasma glucose levels and type 2 diabetes risk. Nabila Bouatia-Naji et al. Nature Genetics Published online: 7 December 2008, doi:10.1038/ng.277

There’s an excellent translation of what this study means, translated into layman’s terms at Science Daily:

Body Clock Linked to Diabetes And High Blood Sugar In New Genome-wide Study

 

The Environmental Factors That Push Borderline Genes into Full-fledged Diabetes

We’ve seen so far that to get Type 2 Diabetes you seem to need to have some diabetes gene or genes, but that not everyone with these genes develops diabetes. There are what scientists call environmental factors that can push a borderline genetic case into full fledged diabetes. Let’s look now at what the research has found about what some of these environmental factors might be.

 

Your Mother’s Diet During Pregnancy May Have Caused Your Diabetes

Many “environmental factors” that scientists explore occur in the environment of the womb. Diabetes is no different, and the conditions you experienced when you were a fetus can have life-long impact on your blood sugar control.

Researchers following the children of mothers who had experienced a Dutch famine during World War II found that children of mothers who had experienced famine were far more likely to develop diabetes in later life than a control group from the same population whose mothers had been adequately fed.

Glucose tolerance in adults after prenatal exposure to famine. Ravelli AC et al.Lancet. 1998 Jan 17;351(9097):173-7.,

A study of a Chinese population found a link between low birth weight and the development of both diabetes and impaired glucose regulation (i.e. prediabetes) that was independent of “sex, age, central obesity, smoking status, alcohol consumption, dyslipidemia, family history of diabetes, and occupational status.” Low birth weight in this population may well be due to less than optimal maternal nutrition during pregnancy.

Evidence of a Relationship Between Infant Birth Weight and Later Diabetes and Impaired Glucose Regulation in a Chinese Population Xinhua Xiao et. al. Diabetes Care31:483-487, 2008.

This may not seem all that relevant to Americans whose mothers have not been exposed to famine conditions. But to conclude this is to forget how many American teens and young women suffer from eating disorders and how prevalent crash dieting is in the group of women most likely to get pregnant.

It is also true that until the 1980s obstetricians routinely warned pregnant women against gaining what is now understood to be a healthy amount of weight. When pregnant women started to gain weight, doctors often put them on highly restrictive diets which resulted in many case in the birth of underweight babies.

Your Mother’s Gestational Diabetes May Have Caused Your Diabetes

Maternal starvation is not the only pre-birth factor associated with an increased risk of diabetes. Having a well-fed mother who suffered gestational diabetes also increases a child’s risk both of obesity and of developing diabetes.

High Prevalence of Type 2 Diabetes and Pre-Diabetes in Adult Offspring of Women With Gestational Diabetes Mellitus or Type 1 Diabetes The role of intrauterine hyperglycemia Tine D. Clausen, MD et al. Diabetes Care 31:340-346, 2008

Pesticides and PCBs in Blood Stream Correlate with Incidence of Diabetes

A study conducted among members of New York State’s Mohawk tribe found that the odds of being diagnosed with diabetes in this population was almost 4 times higher in members who had high concentrations of PCBs in their blood serum. It was even higher for those with high concentrations of pesticides in their blood.

Diabetes in Relation to Serum Levels of Polychlorinated Biphenyls and Chlorinated Pesticides in Adult Native Americans Neculai Codru, Maria J. Schymura,Serban Negoita,Robert Rej,and David O. Carpenter.Environ Health Perspect. 2007 October; 115(10): 1442-1447.Published online 2007 July 17. doi: 10.1289/ehp.10315.

It is very important to note that there is no reason to believe this phenomenon is limited to people of Native American heritage. Upstate NY has a well-known and very serious PCB problem–remember Love Canal? And the entire population of the U.S. has been overexposed to powerful pesticides for a generation.

More evidence that obesity may be caused by exposure to toxic pollutants which damage genes comes in a study published January of 2009. This study tracked the exposure of a group of pregnant Belgian woman to several common pollutants: hexachlorobenzene, dichlorodiphenyldichloroethylene (DDE) , dioxin-like compounds, and polychlorinated biphenyls (PCBs). It found a correlation between exposure to PCBs and DDE and obesity by age 3, especially in children of mothers who smoked.

Intrauterine Exposure to Environmental Pollutants and Body Mass Index during the First 3 Years of Life Stijn L. Verhulst et al., Environmental Health Perspectives. Volume 117, Number 1, January 2009

These studies, which garnered no press attention at all, probably have more to tell us about the reason for the so-called “diabetes epidemic” than any other published over the last decade.

BPA and Plasticizers from Packaging Are Strongly Linked to Obesity and Insulin Resistance

BPA, the plastic used to line most metal cans has long been suspected of causing obesity. Now we know why. A study published in 2008 reported that BPA suppresses a key hormone, adiponectin, which is responsible for regulating insulin sensitivity in the body and puts people at a substantially higher risk for metabolic syndrome.

Science Daily: Toxic Plastics: Bisphenol A Linked To Metabolic Syndrome In Human Tissue

The impact of BPA on children is dramatic. Analysis of 7 years of NHANES epidemiological data found that having a high urine level of BPA doubles a child’s risk of being obese.

Bisphenol A and Chronic Disease Risk Factors in US Children. Eng, Donna et al.Pediatrics Published online August 19, 2013. doi: 10.1542/peds.2013-0106

You, and your children are getting far more BPA from canned foods than what health authorities assumed they were getting. A research report published in 2011 reported that the level of BPA actually measured in people’s bodies after they consumed canned soup turned out to be extremely high. People who ate a serving of canned soup every day for five days had BPA levels of 20.8 micrograms per liter of urine, whereas people who instead ate fresh soup had levels of 1.1 micrograms per liter.

Canned Soup Consumption and Urinary Bisphenol A: A Randomized Crossover Trial Carwile, JL et al. JAMA. November 23/30, 2011, Vol 306, No. 20

Nevertheless, the FDA caved in to industry pressure in 2012 and refused to regulate BPA claiming that, as usual, more study was needed. (FDA: BPA)

BPA is not the only toxic chemical associated with plastics that may be promoting insulin resistance. . Phthalates are compounds added to plastic to make it flexible. They rub off on our food and are found in our blood and urine. A study of 387 Hispanic and Black, New York City children who were between six and eight years old measured the phthalates in their urine and found that the more phthalates in their urine, the fatter the child was a year later.

Associations between phthalate metabolite urinary concentrations and body size measures in New York City children.
Susan L. Teitelbaum et al.Environ Res. 2012 Jan;112:186-93.

This finding was echosed by another study:

Urinary phthalates and increased insulin resistance in adolescents Trasande L, et al. Pediatrics 2013; DOI: 10.1542/peds.2012-4022.

And phthalates are everywhere. A study of 1,016 Swedes aged 70 years and older found that four phthalate metabolites were detected in the blood serum of almost all the participants. High levels of three of these were associated with the prevalence of diabetes. The researchers explain that one metabolite was mainly related to poor insulin secretion, whereas two others were related to insulin resistance. The researchers didn’t check to see whether this relationship held for prediabetes.

Circulating Levels of Phthalate Metabolites Are Associated With Prevalent Diabetes in the Elderly.Lind, MP et al. Diabetes. Published online before print April 12, 2012, doi: 10.2337/dc11-2396

Chances are very good that these same omnipresent phthalates are also causing insulin resistance and damaging insulin secretion in people whose ages fall between those of the two groups studied here.

Use of Herbicide Atrazine Maps to Obesity, Causes Insulin Resistance

A study published in April of 2009 mentions that “There is an apparent overlap between areas in the USA where the herbicide, atrazine (ATZ), is heavily used and obesity-prevalence maps of people with a BMI over 30.”

It found that when rats were given low doses of this pesticide in thier water, “Chronic administration of ATZ decreased basal metabolic rate, and increased body weight, intra-abdominal fat and insulin resistance without changing food intake or physical activity level.” In short the animals got fat even without changing their food intake. When the animals were fed a high fat,high carb diet, the weight gain was even greater.

Insulin resistance was increased too, which if it happens in people, means that people who have genetically-caused borderline capacity to secrete insulin are more likely to become diabetic when they are exposed to this chemical via food or their drinking water.

Chronic Exposure to the Herbicide, Atrazine, Causes Mitochondrial Dysfunction and Insulin Resistance PLoS ONE Published 13 Apr 2009

2,4-D A Common Herbicide Blocks Secretion of GLP-1–A Blood Sugar Lowering Gastric Peptide

In 2007 scientists at New York’s Mount Sinai Hospital discovered that the intestine has receptors for sugar identical to those found on the tongue and that these receptors regulate secretion of glucagon-like peptide-1 (GLP-1). GLP-1 is the peptide that is mimicked by the diabetes drug Byetta and which is kept elevated by Januvia and Onglyza. You can read about that finding in this Science Daily report:

Science Daily: Your Gut Has Taste Receptors

In November 2009, these same scientists reported that a very common herbicide 2,4 D blocked this taste receptor, effectively turning off its ability to stimulate the production GLP-1. The fibrate drugs used to lower cholesterol were also found to block the receptor.

Science Daily: Common Herbicides and Fibrates Block Nutrient-Sensing Receptor Found in Gut and Pancreas

What was even more of concern was the discovery that the ability of these compounds to block this gut receptor “did not generalize across species to the rodent form of the receptor.” The lead researcher was quoted as saying,

…most safety tests were done using animals, which have T1R3 receptors that are insensitive to these compounds,

This takes on additional meaning when you realize that most compounds released into the environment are tested only on animals, not humans. It may help explain why so many supposedly “safe” chemicals are damaging human glucose metabolisms.

Trace Amounts of Arsenic in Urine Correlate with Dramatic Rise in Diabetes

A study published in JAMA in August of 2008 found of 788 adults who had participated in the 2003-2004 National Health and Nutrition Examination Survey (NHANES) found those who had the most arsenic in their urine, were nearly four times more likely to have diabetes than those who had the least amount.

The study is reported here:

Arsenic Exposure and Prevalence of Type 2 Diabetes in US Adults. Ana Navas-Acien et al. JAMA. 2008;300(7):814-822.

The New York Times report about this study (no longer online) added this illuminating bit of information to the story:

Arsenic can get into drinking water naturally when minerals dissolve. It is also an industrial pollutant from coal burning and copper smelting. Utilities use filtration systems to get it out of drinking water.

Seafood also contains nontoxic organic arsenic. The researchers adjusted their analysis for signs of seafood intake and found that people with Type 2 Diabetes had 26 percent higher inorganic arsenic levels than people without Type 2 Diabetes.

How arsenic could contribute to diabetes is unknown, but prior studies have found impaired insulin secretion in pancreas cells treated with an arsenic compound.

Prescription Drugs, Especially SSRI Antidepressants Cause Obesity and Possibly Diabetes

Another important environmental factor is this: Type 2 Diabetes can be caused by some commonly prescribed drugs. Beta blockers and atypical antipsychotics like Zyprexa have been shown to cause diabetes in people who would not otherwise get it. This is discussed here.

There is some research that suggests that SSRI antidepressants may also promote diabetes. It is well known that antidepressants cause weight gain.

Spin doctors in the employ of the drug companies who sell these high-profit antidepressants have long tried to attribute the relationship between depression and obesity to depression, rather than the drugs used to treat the condition.

However, a new study published in June 2009 used data from the Canadian National Population Health Survey (NPHS), a longitudinal study of a representative cohort of household residents in Canada and tracked the incidence of obesity over ten years.

The study found that, “MDE [Major Depressive Episode] does not appear to increase the risk of obesity. …Pharmacologic treatment with antidepressants may be associated with an increased risk of obesity. [emphasis mine]. The study concluded,

Unexpectedly, significant effects were seen for serotonin-reuptake-inhibiting antidepressants [Prozac,Celexa, Lovox, Paxil, Zoloft] and venlafaxine [Effexor], but neither for tricyclic antidepressants nor antipsychotic medications.

Scott B. Patten et al. Psychother Psychosom 2009;78:182-186 (DOI: 10.1159/000209349)

Here is an article posted by the Mayo Clinic that includes the statement “weight gain is a reported side effect of nearly all antidepressant medications currently available.

Antidepressants and weight gain – Mayoclinic.com

Here is a report about a paper presented at the 2006 ADA Conference that analyzed the Antidepressant-Diabetes connection in a major Diabetes prevention study:

Medscape: Antidepressant use associated with increased type 2 diabetes risk.

Treatment for Cancer, Especially Radiation, Greatly Increases Diabetes Risk Independent of Obesity or Exercise Level

A study published in August 2009 analyzed data for 8599 survivors in the Childhood Cancer Survivor Study. It found that after adjusting for body mass and exercise levels, survivors of childhood cancer were 1.8 times more likely than the siblings to report that they had diabetes.

Even more significantly, those who had had full body radiation were 7.2 times more likely to have diabetes.

This raises the question of whether exposure to radiation in other contexts also causes Type 2 diabetes.

Diabetes Mellitus in Long-term Survivors of Childhood Cancer: Increased Risk Associated With Radiation Therapy: A Report for the Childhood Cancer Survivor Study.Lillian R. Meacham et al. Arch. Int. Med.Vol. 169 No. 15, Aug 10/24, 2009.

More Insight into the Effect of Genetic Flaws

Now that we have a better idea of some of the underlying physiological causes of diabetes, lets look more closely at the physiological processes that takes place as these genetic flaws push the body towards diabetes.

Insulin Resistance Develops in Thin Children of People with Type 2 Diabetes

Lab research has come up with some other intriguing findings that challenge the idea that obesity causes insulin resistance which causes diabetes. Instead, it looks like the opposite happens: Insulin resistance precedes the development of obesity.

One of these studies took two groups of thin subjects with normal blood sugar who were evenly matched for height and weight. The two groups differed only in that one group had close relatives who had developed Type 2 Diabetes, and hence, if there were a genetic component to the disorder, they were more likely to have it. The other group had no relatives with Type 2 Diabetes. The researchers then and examined the subjects’ glucose and insulin levels during a glucose tolerance test and calculated their insulin resistance. They found that the thin relatives of the people with Type 2 Diabetes already had much more insulin resistance than did the thin people with no relatives with diabetes.

Insulin resistance in the first-degree relatives of persons with Type 2 Diabetes. Straczkowski M et al. Med Sci Monit. 2003 May;9(5):CR186-90.

This result was echoed by a second study published in November of 2009.

That study compared detailed measurements of insulin secretion and resistance in 187 offspring of people diagnosed with Type 2 diabetes against 509 controls. Subjects were matched with controls for age, gender and BMI. It concluded:

The first-degree offspring of type 2 diabetic patients show insulin resistance and beta cell dysfunction in response to oral glucose challenge. Beta cell impairment exists in insulin-sensitive offspring of patients with type 2 diabetes, suggesting beta cell dysfunction to be a major defect determining diabetes development in diabetic offspring.

Beta cell (dys)function in non-diabetic offspring of diabetic patients M. Stadler et al. Diabetologia Volume 52, Number 11 / November, 2009, pp 2435-2444. doi 10.1007/s00125-009-1520-7

Mitochondrial Dysfunction is Found in Lean Relatives of People with Type 2 Diabetes

One reason insulin resistance might precede obesity was explained by a landmark 2004 study which looked at the cells of the “healthy, young, lean” but insulin-resistant relatives of people with Type 2 Diabetes and found that their mitochondria, the “power plant of the cells” that is the part of the cell that burns glucose, appeared to have a defect. While the mitochondria of people with no relatives with diabetes burned glucose well, the mitochondria of the people with an inherited genetic predisposition to diabetes were not able to burn off glucose as efficiently, but instead caused the glucose they could not burn and to be stored in the cells as fat.

Impaired mitochondrial activity in the insulin-resistant offspring of patients with type 2 diabetes. Petersen KF et al. New England J Med 2004 Feb 12; 350(7);639-41

More Evidence that Abnormal Insulin Resistance Precedes Weight Gain and Probably Causes It

A study done by the same researchers at Yale University School of Medicine who discovered the mitochondrial problem we just discussed was published in Proceedings of the National Academy of Science (PNAS) in July 2007. It reports on a study that compared energy usage by lean people who were insulin resistant and lean people who were insulin sensitive.

The role of skeletal muscle insulin resistance in the pathogenesis of the metabolic syndrome Petersen,KF et al. PNAS July 31, 2007 vol. 104 no. 31 12587-12594.

Using new imaging technologies, the researchers found that lean but insulin resistant subjects converted glucose from high carbohydrate meals into triglycerides–i.e. fat. Lean insulin-sensitive subjects, in contrast, stored the same glucose in the form of muscle and liver glycogen.

The researchers conclude that:

the insulin resistance, in these young, lean, insulin resistant individuals, was independent of abdominal obesity and circulating plasma adipocytokines, suggesting that these abnormalities develop later in the development of the metabolic syndrome.”

In short, obesity looked to be a result, not a cause of the metabolic flaw that led these people to store carbohydrate they ate in the form of fat rather than burn it for energy.

The researchers suggested controlling insulin resistance with exercise. It would also be a good idea for people who are insulin resistant, or have a family history of Type 2 Diabetes to cut back on their carb intake, knowing that the glucose from the carbs they eat is more likely to turn into fat.

Beta Cells Fail to Reproduce in People with Diabetes

A study of pancreas autopsies that compared the pancreases of thin and fat people with diabetes with those of thin and fat normal people found that fat, insulin-resistant people who did not develop diabetes apparently were able to grow new beta-cells to produce the extra insulin they needed. In contrast, the beta cells of people who developed diabetes were unable to reproduce. This failure was independent of their weight.

Beta-Cell Deficit and Increased Beta-Cell Apoptosis in Humans With Type 2 Diabetes. Alexandra E. Butler, et al. Diabetes 52:102-110, 2003

Once Blood Sugars Rise They Impair a Muscle Gene that Regulates Insulin Sensitivity

Another piece of the puzzle falls into place thanks to a research study published on Feb 8, 2008.

Downregulation of Diacylglycerol Kinase Delta Contributes to Hyperglycemia-Induced Insulin Resistance. Alexander V. Chibalin et. al. Cell, Volume 132, Issue 3, 375-386, 8 February 2008.

As reported in Diabetes in Control (which had access to the full text of the study)

The research team identified a “fat-burning” gene, the products of which are required to maintain the cells insulin sensitivity. They also discovered that this gene is reduced in muscle tissue from people with high blood sugar and type 2-diabetes. In the absence of the enzyme that is made by this gene, muscles have reduced insulin sensitivity, impaired fat burning ability, which leads to an increased risk of developing obesity.

“The expression of this gene is reduced when blood sugar rises, but activity can be restored if blood sugar is controlled by pharmacological treatment or exercise”, says Professor Juleen Zierath. “Our results underscore the importance of tight regulation of blood sugar for people with diabetes.”

In short, once your blood sugar rises past a certain point, you become much more insulin resistant. This, in turn, pushes up your blood sugar more.

A New Model For How Diabetes Develops

These research findings open up a new way of understanding the relationship between obesity and diabetes.

Perhaps people with the genetic condition underlying Type 2 Diabetes inherit a defect in the beta cells that make those cells unable to reproduce normally to replace cells damaged by the normal wear and tear of life.Or perhaps exposure to an environmental toxin damages the related genes.

Perhaps, too, a defect in the way that their cells burn glucose inclines them to turn excess blood sugar into fat rather than burning it off as a person with normal mitochondria might do.

Put these facts together and you suddenly get a fatal combination that is almost guaranteed to make a person fat.

Studies have shown that blood sugars only slightly over 100 mg/dl are high enough to render beta cells dysfunctional.

Beta-cell dysfunction and glucose intolerance: results from the San Antonio metabolism (SAM) study. Gastaldelli A, et al. Diabetologia. 2004 Jan;47(1):31-9. Epub 2003 Dec 10.

In a normal person who had the ability to grow new beta cells, any damaged beta cells would be replaced by new ones, which would keep the blood sugar at levels low enough to avoid further damage. But the beta cells of a person with a genetic heritage of diabetes are unable to reproduce So once blood sugars started to rise, more beta cells would succumb to the resulting glucose toxicity, and that would, in turn raise blood sugar higher.

As the concentration of glucose in their blood rose, these people would not be able to do what a normal person does with excess blood sugar–which is to burn it for energy. Instead their defective mitochondria will cause the excess glucose to be stored as fat. As this fat gets stored in the muscles it causes the insulin resistance so often observed in people with diabetes–long before the individual begins to gain visible weight. This insulin resistance puts a further strain on the remaining beta cells by making the person’s cells less sensitive to insulin. Since the person with an inherited tendency to diabetes’ pancreas can’t grow the extra beta cells that a normal person could grow when their cells become insulin resistant this leads to ever escalating blood sugars which further damage the insulin-producing cells, and end up in the inevitable decline into diabetes.

Low Fat Diets Promote the Deterioration that Leads to Diabetes in People with the Genetic Predisposition

In the past two decades, when people who were headed towards diabetes begin to gain weight, they were advised to eat a low fat diet. Unfortunately, this low fat diet is also a high carbohydrate diet–one that exacerbates blood sugar problems by raising blood sugars dangerously high, destroying more insulin-producing beta-cells, and catalyzing the storage of more fat in the muscles of people with dysfunctional mitochondria. Though they may have stuck to diets to low fat for weeks or even months these people were tormented by relentless hunger and when they finally went off their ineffective diets, they got fatter. Unfortunately, when they reported these experiences to their doctors, they were almost universally accused of lying about their eating habits.

It has only been documented in medical research during the past two years that that many patients who have found it impossible to lose weight on the low fat high carbohydrate can lose weight–often dramatically–on a low carbohydrate diet while improving rather than harming their blood lipids.

Very low-carbohydrate and low-fat diets affect fasting lipids and postprandial lipemia differently in overweight men. Sharman MJ, et al. J Nutr. 2004 Apr;134(4):880-5.

An isoenergetic very low carbohydrate diet improves serum HDL cholesterol and triacylglycerol concentrations, the total cholesterol to HDL cholesterol ratio and postprandial lipemic responses compared with a low fat diet in normal weight, normolipidemic women. Volek JS, et al. J Nutr. 2003 Sep;133(9):2756-61.

The low carb diet does two things. By limiting carbohydrate, it limits the concentration of blood glucose which often is enough to bring moderately elevated blood sugars down to normal or near normal levels. This means that there will be little excess glucose left to be converted to fat and stored.

It also gets around the mitochondrial defect in processing glucose by keeping blood sugars low so that the body switches into a mode where it burns ketones rather than glucose for muscle fuel.

Relentless Hunger Results from Roller Coaster Blood Sugars

There is one last reason why you may believe that obesity caused your diabetes, when, in fact, it was undiagnosed diabetes that caused your obesity.

Long before a person develops diabetes, they go through a phase where they have what doctors called “impaired glucose tolerance.” This means that after they eat a meal containing carbohydrates, their blood sugar rockets up and may stay high for an hour or two before dropping back to a normal level.

What most people don’t know is that when blood sugar moves swiftly up or down most people will experience intense hunger. The reasons for this are not completely clear. But what is certain is that this intense hunger caused by blood sugar swings can develop years before a person’s blood sugar reaches the level where they’ll be diagnosed as diabetic.

This relentless hunger, in fact, is often the very first diabetic symptom a person will experience, though most doctors do not recognize this hunger as a symptom. Instead, if you complain of experiencing intense hunger doctors may suggest you need an antidepressant or blame your weight gain, if you are female, on menopausal changes.

This relentless hunger caused by impaired glucose tolerance almost always leads to significant weight gain and an increase in insulin resistance. However, because it can take ten years between the time your blood sugar begins to rise steeply after meals and the time when your fasting blood sugar is abnormal enough for you to be diagnosed with diabetes, most people are, indeed, very fat at the time of diagnosis.

With better diagnosis of diabetes (discussed here) we would be able to catch early diabetes before people gained the enormous amounts of weight now believed to cause the syndrome. But at least now people with diabetic relatives who are at risk for developing diabetes can go a long way towards preventing the development of obesity by controlling their carbohydrate intake long before they begin to put on weight.

You CAN Undo the Damage

No matter what your genetic heritage or the environmental insults your genes have survived, you can take steps right now to lower your blood sugar, eliminate the secondary insulin resistance caused by high blood sugars, and start the process that leads back to health. The pages linked here will show you how.

How To Get Your Blood Sugar Under Control

What Can You Eat When You Are Cutting The Carbs?

What is a Normal Blood Sugar

Research Connecting Blood Sugar Level with Organ Damage

The 5% Club: They Normalized Their Blood Sugar and So Can You

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